I did a search a couple of years ago and found a site that showed how to do a trigger job on an AR for no money. I worked on my AR 10 and it made a heck of an improvement. Its probably not as good as a single stage drop in trigger, but it's better then the OE trigger.
BTW whats the deal with 2 stage triggers, for hundreds of years the norm was a single stage triggers on sporting guns. I see no advantage to a 2 stage trigger.