So after doing some further searching and fiddling, I went back to the Trek store to look at the 520. However, their base model was 1400 bucks, which is really just a lot more than I wanted to spend at once. So I was looking at the 7.5FX again and the Trek guy told me I want to avoid it because of the carbon fork and the inability to mount a rack or panniers on it if I plan on touring across the country (~3400 miles). He also mentioned the Nebula seat post, while nice for commuting, weighs quite a bit and isn't necessary.
So what suggested was to get a 7.3 FX, and gradually change out all of the components over the next 8 months. He mentioned a few dealers he knows off E-Bay that sell only brand new parts for a pretty decent price, so since he was talking me out of spending more in his store he really genuinely seemed to be trying to help me rather than screw me (which is why I love my local Trek store). I really enjoyed the feel of this bike and felt very, very comfortable on it, so I can still train on it and commute to work and stuff, and by the time I'm leaving for my tour on it I can have the admittedly bad components all changed out.
So, the guy suggested I get the following components switched out between now in August, in order of importance. What I'm looking for from you fine folks is suggestions on what specifics stuff to look for, for this model bike. http://www.trekbikes.com/us/en/bikes/road/fx/73fx/
Wheels: He said this is by far the important thing to get upgraded. From what I've read here, a 700c wheel with 36 spokes is what I'm looking for, right? That seems like pretty much it, this didn't seem too complicated.
Saddle: I'm just getting a Brooks saddle. This seems like a no brainer from perusing the touring forums here.
Front Crank: He said the one in the stock 7.3FX is more geared for the road and isn't all that great quality, and told me to find a better quality one that's geared better for touring. Any ideas what I'm looking for here?
Rear Casette: He said get a 9 speed. My current one is an 8 speed. I'm also assuming the choice of cassette is going to dictated by what crank I get, right?
Chain: He said get two chains, they're so cheap and not that heavy that it'd be better to have a spare in case one breaks in the middle of nowhere. He didn't specify, but are there different kinds of chains, or are bike chains pretty universal?
Shifters: Since I'm switching from 8 to 9 speeds in the back, I'm assuming I'll need new shifters as well. I have no idea what kind to get.
Front Derailleur: Right now the stock model is a C102. I'm assuming just switch it our for something a bit nicer because I have no idea where that is on Shimano's hierarchy. Front Derailleurs seem REALLY cheap for some reason, as well.
So yeah, that's it. Since I'm basically swapping out everything other than the rear derailleur (a vanilla Deore one, which the guy said should be fine for this) I can basically build this thing any way I want. Suggestions are most appreciated!