Welcome Y'all!!
STAY AWAY FROM THE DENTON SCUBA PARK!!! It's about 120' long by 30' wide by 15' deep with about 2" vis!(I'm serious - I could barely see my flashlight when I stuck it in my own face)
Your best bets are PK and Lake Whitney. PK has better vis and is deeper, but it's also colder and you pretty much need a boat to get away from the crowd. You can also try Lake Murray in Oklahoma, since you're up in Decatur. It's off I35 just north of the border . I don't know if they still have an air shop though - maybe one of our Red River Bros can help.
Whitney charges $5 + $5 for airfills. I'm not sure if PK charges since we always take a boat. Their airfills are $3-$5, depending on how much air you need. Athens ($25 + $5 air)is a clay pond that all the Dallas area shops use for thier OW cert dives. It's only 25' deep, but they have lots of cool stuff sunk there, a big jet you can swim through, a school bus, lots of boats, a couple of tunnels etc. All 3 places are run by real friendly folks.
Almost forgot! There's also an old missle silo out by Midland. They only open for groups, but lots of LDS do trips out there.
Enough rambling. (My dive buddy called to say he can't go this weekend and I'm jonesin' real bad)
Hope to see ya down under!! (No, not there, but that would be cool too)