I have Jewell, Chip McCormick, RRA (2-stage), Timney triggers in almost all my AR's. They are head over heels improvement on anything the factory puts in. The McCormick and the Timney triggers are virtually drop in replacements, even though they suggest you take it to a gunsmith to do. If you can pull and replace a couple pins, you can do it yourself. Afterwards, a simple safety check to insure everything is functional and you are ready to go. The Jewell triggers are like the RRA, in kit form. You might find that a little more challenging, but check online for step-by-step instructions and even that is do-able.
Depending on the kind of shooting you do most, single stage triggers seem to be preferred for tactical, home defense, where you won't be spending alot of time prepping for a shot but need a quick clean break. Not that you can't. 2-stage triggers are set up more for the target type shooter, where you take the time to feel the take-up, then the break. Again, not that you can't use the 2-stage for home defense or taking over a 3rd world country.