I just recently purchased and assembled one of J&T's 16" Complete CAR Kits. Excellent product in my opinion. Professional packaging with copy of order, credit card receipt, and catalog. Extemely friendly and helpful over the phone. I would purchase from J&T again.
Upper is shipped assembled and ready to go. You will receive the components for the lower receiver. I had to review various parts diagrams online to figure the different springs, pins, etc. If it helps, I had never held, fired, or even thought about an AR15 two months ago.
Fired 100 rounds through it breaking in barrel and no problems other than on one round (Remington UMC) the firing pin did not contact the primer hard enough, so round did not fire. Not sure exactly what happen. It was the second round in mag.
I used the following tools:
Small lightweight hammer
Tape (to protect finish on LR, specifically installing bolt catch)
Spanner wrench for CAR type stock
Time: 60 minutes by myself. I would recommend
a second body to make life easier :)
Also, a pivot pin installation makes life easier but doable without it.
Go for it and just post questions if you need any help.