Well there are a couple of Guitar Center superstore here. As far a independent shops there are too many to list, just check the yellow pages. Same way with nightclubs we have tons and tons, many that feature live music.
Here Is the GuideLive list of music events next week, I see Clapton, Gladys Knight and Chuck Mangione will be in town amongst others
GuideLive.com is a wealth of information, you may want to check out more on that site.
You may want to check out:
The Ball Park in Arlington, Six Flags over Texas, and the construction site for the new Cowboys mega stadium (all located right together)
AAC (American Airlines Center)
Reunion Tower
The Nokia Theatre in Grand Prarie and Lone Star Park(Class A horse track)
The West end (cool clubs, and the Kennedy museum at Dealey plaza, etc...)
If you like old west stuff take a trip over to the Fort Worth Stockyards area