Shops I've used:
Don Johle's Bike World, on Broadway (Beltline) in Garland, a half mile or so off of I-30. They deal with a wide range of bikes, not just road bikes. That's where I bought my Sojourn and they do most of the work on it.
Plano Cycling and Fitness in Plano- more geared towards road bikes, etc.
Texoma Bicycle in Sherman- They deal with a wide range of bikes. That's where I bought my tandem.
There's a pretty decent bike shop in Rockwall, but I've not really used it for anything. I've shopped some at Bicycles Inc and Richardson Bike Mart, but haven't used their services any.