The set up you mentioned will make a fine AR.
As far as trigger:
For milspec, I have been looking at the ALG Defense trigger. They are associated with Geissele. It is a mil-spec'ish trigger, 4.5-5.5lbs. From what i read it is a quality trigger that is very smooth. Some shooters are getting the ALG trigger and adding JP reduced power springs. $65 at Aim Surplus.
I have 3 ARs with milspec fire control groups with JP reduced power springs. They all work great. Pull is around 4lbs. $40 with JP springs.
I have a 3 gun AR with a Timney 3lbs. It is awesome. No creap, no travel, breaks real clean and it is easy to install. $150+ depending on model.
Other triggers i would look at is the Geissele S3G for a single stage, the several Geissele 2 stages and the RRA 2 stage.
Edit: If you go with a milspec trigger, the only mod i would do is JP springs. I wouldn't recommend polishing the trigger and hammer. Some have done it with success, some have failed.