It's not that hard. Particularly if you have a few weeks, cause you're bound to forget some small parts that will cause you some delays.
The most difficult things involve the "press fit" type parts, like the headset. In fact, the headset might be the only hard part.
Actually, getting your derailers set up is the worst part. Excellent motivation to go single speed, if you ask me.
After the frame, your biggest expense will be your fork. You won't be able to reuse one you have sitting around (assuming you don't have any other 29 wheel bikes). You'll need the correct fork (find out what axle to crown dimension your frame is built for, and buy the best fork you can afford for that size, +/- 10 mm - oh you also need to match fork steerer tube to the frame, although you may have some options in headsets such as a 1 1/8 fork can work in a 1 1/2 headtube with the right headset, but NOT the other way around!!!).
How to determine the best fork...uh, well good luck. Don't rule out companies not named Fox...
After the fork, the biggest expense is the wheels. Well, I guess that depends on your budget. But the key to wheels is the front hub has to match your fork (9mm, 15mm, or 20mm axle). You can ignore the back hub dimensions and get those right about 98% of the time - I'm not even sure 29ers stray into different hub dimensions. There are some variations for 26" wheels, basically wider for the all mountain/freeride market.
Anyway, a stand is incredibly helpful, even a homemade one out of 2x4s like mine is. You don't need much for tools even. Well you'll need a couple specialized items, bottom bracket cup wrench, cassette chain wrench, maybe a crown race installer thingie (I use a ghetto version with a couple wood clamps), headset press (don't think my method of "find the biggest hammer you can" would be appropriate for a carbon frame)...can't think of anything else right at the comment.
LBS will do partial install tasks...like if you are comfortable with 98% of the work, they are willing to do the other 2%. You might even be money ahead if you need a special tool to do something.
So yeah sizes you need from your frame:
BB shell width/style
If you are doing this to save money, good luck. The small parts add up quick. If you are doing it to get the bike you REALLY want, you are on the right track!
I built my Banshee up in 2 easy nights of work (after all 3 kids were put to bed). It's my second frame up build.
Here's my bare frame:
After 1 night of work (missing cranks, pedals, etc)
After night 2, ready to ride