I’m highly considering a 9mm RRA upper complete with bcg for $300 shipped…upper and bcg is said to be NEW.
What other parts would I need and their approximate cost?
You’ll get more if you ask about 9mm in the pistol caliber section 
That’s a good price I suppose.
Mag block and mags…
Lower that will work with the bolt- or you can install a 9mm hammer.
Will do…moving to pistol section!!!