I've bought from Surplus Ammo & Arms and they are a standup company. Very courteous, at least a couple years ago. Haven't tried them lately.
Sorry, I have no experience with that rifle though...
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek