All I can say is hang on to family heirlooms. The day will come when you'll hate yourself for selling grandpa's 100 year old gun. I rarely sell a firearm, I try to buy quality then hang on to them.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek