Is there a such thing as an honest car dealer? That being said, I used Eldorado in McKinney.
For parts, most of the guys around here order their parts online.
Rosenthal
Mazda South, Austin TX
Or if you can prove you are in a racing organization (SCCA Autocross, etc.)
http://www.mazdamotorsports.com/
For Repairs, Rogue is the guy that all the guys here trust their cars to.