Bicycle Mechanics - 19" Giant Yukon

I hope this is in the right section...
Alrighty, first off, my knowledge of bikes is limited to how they work, so I have no familiarity with the market.

Okey dokey, I have a Giant Yukon with a 19" frame (as the title might suggest) but I got it used, so I have no idea what year it is; I think it's newish. If it helps at all, it has disc brakes and 24 gears. So... someone stole most of it and I am now 2 wheels and 1 seat short of not using my sister's bike, and professional repairs would be in the neighborhood of $400. So, my question to you gentlemen, is how much could I save if I fixed it myself? Links to compatible hardware would be much appriciated.

Yeah... you could save a bundle by buying new wheels and seat online and installing them yourselves. I had to replace a stolen set of MTB wheels a couple of years ago, and got a very high-quality set on sale from Performance Bike for about $110. You can get 3 inner tubes for about $10. And then maybe $20-30 for a cheap but decent set of tires (depends on if you want slicks or knobbies). Then, probably $20 for a run-of-the-mill seatpost and $20 for a saddle. So I'd guess if you buy everything online from PerformanceBike, Nashbar, PricePoint, or JensonUSA, you can get it all for less than $200. You'll also need allen wrenches and tire levers to install everything assuming no other repairs are needed.

Alrighty, awesome. Uhh, I guess I forgot to say this, but a bigger problem is what's compatible. I have no idea what size of anything to get. Thanks a ton though, moxfyre. I'm that much closer :)

Alrighty, awesome. Uhh, I guess I forgot to say this, but a bigger problem is what's compatible. I have no idea what size of anything to get. Thanks a ton though, moxfyre. I'm that much closer :)
Well... you're looking for a 26" MTB wheelset with *disc hubs* and an 8/9/10-speed Shimano freehub. Does that help? :) You'll need an 8-speed cassette too, probably a wide-range MTB cassette is preferably (something like 12-28 would be good).

For the saddle, any saddle made in the last few decades will do. For the seatpost, you need to figure out what size seatpost your frame takes. This can be rather tricky. You can get a pretty good idea by measuring the interior diameter of the seat tube with calipers, but to get it right you'll probably have to take it to a shop and have them try several sizes of seatposts.

If you had disk brakes then you will need rotors also.

Alright, I think I'm set :)

Thanks a ton, guys :D