1) NAPA and Kragen/Checker both sell ridiculously inexpensive brake rotors.. Check napaonline.com and partsamerica.com (Kragen), then print out the online prices and go to your local store. They will happily price-match
2) As for pads.. whatever's clever. I like PBR/Axxis for performance use on my MR2s, but on a daily driven Camry not likely to get a lot of maintenance attention, any ol' street pad will probably do fine.
3) I haven't pulled the gas tank out of my Camry yet, but it shouldn't be too nightmarish... If you want it repaired, you're going to have to drain the gasoline first, and then somehow neutralize whatever's left inside and clean it out. I don't think too many shops are going to be eager to weld on a gas tank... Might be better off finding a replacement at a junkyard.
4) That would be a CV (constant velocity) joint. You should be able to get a rebuilt driveshaft/axle for dirt cheap through your local NAPA/Kragen type place. You'll get a core charge refunded when you bring the old axle back, too.

The downside is that replacing these is a bit tougher than doing something like brakes. You'll need, at the least, a good 1/2" drive ratchet and a very large socket to break the axle nut loose so that you can get it out of the hub (30 or 32mm on many Toyotas).. and they're
really torqued on there.. so you'll need some kind of breaker bar extension (2-3 foot long handle off a floor jack usually works well, ha ha!) to get enough leverage.