You don't need anybody to do trigger work for you. AR's are built to be tinkered with. There are several drop in models, that require nothing more than a punch to get the pins out, and a soft hammer to put them back in. Done except for a little adjustment and you can see how to do that on youtube.
Personally, I have the JP trigger systems in all of my AR's that require "fitting". I love making things fit, and knowing I can do a little extra polishing, adjusting, etc. to get it right where I want it.
If you want to do a drop in model, I'd suggest the "anti walk pins". Cheap, just a few bucks, but they will prevent the pins working themselves out of the hole.
I've built a few ar's so getting the trigger out isn't a problem. I don't want problems like light firing after trying to do something I know nothing about.