I was successful replacing both my non-functioning camera, a battery getting on the weak side, and a new back cover (went for one of those colorful back covers sold on eBay). The two things that tripped me up were 1) dealing with that sticky gasket between the antenna and the noise-canceling mic (Step 20), and 2) getting the cover glass to stay put on the new back cover. For 2), I ended up fashioning my own adhesive with 2-sided scotch tape.

*ALSO* You really don't need to do Step 35. Leave the motherboard plugged in, and simply remove and re-attach the camera in place.