Some more info on the particulars would be good -
how much time is this likely to take you (I'd assume 2 days?)
over what kind of ground
how much kit you have to take with you
Because those variables will dictate a lot!
In the meantime - feet and training.
Regarding footwear, whether you choose a pair of approach shoes or boots depends on the ground covered - if it's on roads and hard level surfaces for the most part, maybe consider shoes as they pay dividends in the reduced weight on your feet. Otherwise the support of proper boots may well be neccessary.
It would be counterproductive to suggest a boot (e.g. Garmont "vegan" hiking boots with additional superfeet insoles) to fit your needs because what works for one person may not work for the other.
The best advice anyone should give is to find one or two specialist outdoor shops with a good reputation and be prepared to spend a few hours finding the right pair of boots for you and your aims. Expect the assistant to genuinely know what s/he is on about, but read up a little beforehand to be able to spot the ones who don't. Mention it's for charidee, the other day I heard of someone being given a £150 pair of boots by a shop for similar reasons. More importantly, mention any gait abnormalities you may have.
A good shop will let you try on several kinds of boots on a variety of surfaces and inclines. They may even have a purpose built area to do this.
Make sure that the boots don't rub, pinch and have good room in the toe box so you can wiggle toes, that your heels don't lift from the insole, your ankles have good support. and that they're generally fairly comfy from the off. Take a clean pair of hiking socks to try with your boots. A good shop will have spare pairs for this anyway!
Speaking of socks, this is the neglected half of good footwear. A thinner pair of comfortable hiking socks will serve you much better than a thick pair of socks. Avoid cotton or non-technical nylon socks or ones with big stitching. I don't know if they sell "1000 mile socks" in the US, but give them a miss too. Consider shock-absorbing insoles (like the superfeet I mentioned). They're not obligatory but they may help.
Once you have your boots, the next phase will be to break them in. This is a misnomer - what's mainly happening is that you're being broken in to them! Start out very gently before moving to train in them. Experiment with different lacing patterns to see what's the most comfortable too.
Regarding your feet, if you are prone to problems, then one half may be bad footwear, the other half may be bad footcare. Good progressive training will help, but there are a few tips and tricks and things to avoid.
For example, some people suggest hardening their soles with surgical spirit and such. This can fail spectacularly. Best practice these days is to keep the skin in good condition instead:
*Trim toenails carefully and evenly a few days before your walk
*Wash your feet whenever possible, and dry them thoroughly with a towel, followed by airing them and then talcum powder. You can do this in the field - fill a foot sized ziplock bag with some talc, open, shove foot in, shake some talc on...
*Change socks frequently. Every day of walking, or as soon as they get sweaty or wet.
*Let your feet air as much as possible, even to the extent of hanging them over the edge of your bed/sleeping bag while you sleep.
Taping up feet is a PhD topic in itself. If you planned on something extreme, then you would be best off pre-emptively taping your feet. However it's more likely that the kind of taping needed here is either on problem spots (e.g. if you're prone to heel blisters) or on hot spots (where you're walking along and you feel pain that makes you think you have a blister - it's not likely a blister yet - it's a hot spot!).
There are lots of suggested patterns for taping your feet, but the bottom lines are
1. Use the right kind of tape. Zinc oxide tape, that is. Proper stuff. There are different kinds of it, some of which are crap. In the UK I'd recommend a brand used by the military (Frank Zsameroff, NATO NSN 6510 99 244 0671). Elsewhere, shop around. Basically look for the kinds professional physios use or climbers' tape.
2. Even if you ignore the above, don't use "micropore". Just please - don't! After a few miles you would know why.
3. Apply the tape in such a way that supports the natural movement of your feet, doesn't constrict, but still gives support.
4. Most importantly: make sure the tape goes on smoothly with no wrinkles or rucks. These will become faultlines for fresh blisters.
If the worst comes to the worst, and you get blisters, don't worry. It's only pain. It's likely you will have event medical support along the walk - go see them, especially if you're diabetic as poking around your feet is a no-no. Event medics love it. There's nothing better than the smell of cheesy feet and solvent intermingling with the screams of your patient as OpSite gets sprayed on a crop of blisters. It makes the days of looking after people with soft tissue injuries or bad admin in looking after their electrolyte/fluid balance tolerable.
In training, and otherwise, there are a lot of options out there, ranging from draining the blister and replacing it with tinc-benz (which I think they've banned now as it's possibly carcinogenic and certainly a bit painful) to applying compeed blister plasters.
There's little wrong with compeed, but people just stick them on like normal plasters, they fall off and give them a bad rap. Follow the instructions and they work fine. Anyway, you have two kinds of foot blisters - those which have burst, and those which haven't yet. For both, make sure the general area is clean, dry and crap free - use an antiseptic wipe. For the former, if it's the end of the day, just let them breathe. Otherwise dress them carefully, be it with tape or compeed.
For the former, you can either just do the above on the assumption they will burst eventually or you can burst them yourself. Be careful about that. Personally I normally use the blade of a Leatherman multitool, although professionally one would use a sterile hypodermic needle, introduced laterally and using the bevelled edge to rip the blister lid - merely puncturing it will be insufficient as it will re-seal. Do not take the needle anywhere near inner layers of skin.
Some people puncture it and thread a bit of cotton through to ensure it doesn't re-seal. That's a recipe for the thread to wick in muck from your feet. Don't. Once it's drained, make sure it is cleaned and disinfected, and dress it.
Blisters are a curious topic. They (and treating them) can reduce young men who think themselves the hardest of the hard to gibbering wrecks.
It's funny to watch.
But really they're A) largely preventable and B) a fact of life that they will happen at some point unless you have kevlar feet. It's just pain.
Regarding training - running, cycling, swimming are all good. But nothing will beat a progressive programme of walking (in your event boots), particularly in the kind of conditions you will experience.