Rainier Arms and Mary's Pistols are the two shops that spring to my mind down south. AR15s aren't difficult, as long as you have the appropriate tools. Stripped lowers can be assembled with pretty basic stuff. Assembling an upper is the tricky part, so for a first build, I'd be inclined to suggest a pre-assembled upper. You can buy kits that include everything but a stripped lower starting at around $450 from Del-Ton or DPMS, both of which are decent entry level AR platform weapons. If you want top end gear on a budget (relatively speaking), Bravo Company Machine is the way to go in my opinion.