Actually, I don't think it's that difficult. A friend of mine ordered a back for his 2G, and successfully replaced it. He said it was not very difficult. He recommends using a loupe and making sure you have the proper tools for the tiny screws, and don't loose them like he did!
The back comes with the attached switches. That was actually his reason for replacing the back - the ringer switch had been damaged in a fall and no longer worked. He paid something like $90 on eBay for the back. I thought that was pricey, but it was fully refurbished (all new switches).
In general, serviceability is better with newer iPhones, at least as far as what I have read. My friend commented that after seeing how it's put together, he wouldn't attempt a glass replacement on a 2G, but the back was a snap.