That sounds like a great adventure! The problem is that boot fitting is an art rather than a science--your footstrike (i.e. whether you pronate or supinate) and your foot structure (e.g. arch height, heel/forefoot width) will determine which boots will work for you. (Complicating matters is that there is no industry standard for sizing--some companies tend to run large or vice versa.)
I think the standard advice would be to visit a reputable boot seller (preferably late in the day, since your foot size can increase considerably over time) and simply try on a lot of boots. Ideally, you'll be able to purchase well in advance of your trip in order to get the boots broken in and to be able locate any problem areas you might need to address if you're going long distance under load. You might also consider starting off with an orthotic insert (e.g. Superfit) since most of the OEM inserts are junk to begin with.
Otherwise, I wouldn't go for a bargain basement boot, but don't feel as if you have to pay top dollar for the highest end model either--especially if you're a young guy, since your feet will have a lot more give than those of an older hiker like myself.