vinh- it really is simple. i was surprised at how well my first build went. i just printed the instructions that are tacked at the top of the forum, got an enlarged picture of the parts in the kit (linked from that thread), and went at it. i used a stag lower and an armalite lpk, and i had no troubles, and no modifications were necessary.
i didn't have any trouble w/ the flying detent, either. i just laid the lower on the bench, stuffed the spring in the hole, and put the detent on the spring. then, using the pin, i just pushed the detent down, and slid the pin into its hole. just like that, and i was done. one try (on each lower), and it was uneventful.
i've only shot an ar a couple of times, and never had one apart, so i was pretty sure this would be extremely hard to do, but i had no troubles w/ my first or second build. the hardest part for me was getting the hammer lined up to get the pin in...