Not that difficult if you can get your hands on the tools. I think I spend $180 in tools, so try and borrow them. They go together really easily. The most difficult part is the headspacing. But that only takes 20 minutes at most. This is the info I used to build mine: wecsog.org/fal/carbine/
I bought my receiver from Entreprise. Probably not the best choice, as it required a bit of polishing and fitting to get everything to function smoothly. But they were in stock and I had it in less than a week.
If you can't beat them, join them. Then beat them. If that doesn't work, arrange to have them beaten.