Re: Dallas area gun stores?
+1 for Gunmaster in Plano (on the East side of US75 at Spring Creek parkway, just behind the Sam's club on HWY 5 (K avenue). They have a pretty good collection and lots of consignment stuff and are quite friendly.
Bullet trap is good to and they are on the same road just a few lights south, they are however a bit more of a corporate gun store place these days so I'd visit Gunmaster first then head on down to Bullet Trap.