I was tested for gastroparesis long before I was tested for Celiac's. I have both, and I agree with the nerve damage theory (or at least that is is a probable cause). I have been on Reglan, and quit it for the same reasons as everyone else: dystonic reaction. I was also prescribed Promethazine, but quit that because it made me unable to sleep. I don't believe there have been enough studies on this, in fact, I'm not sure there have been any. However, cutting out gluten did not improve my emptying. It has improved the pain, but not the physical digestion.
I have never had the genetic test, though I really wish I had been, for curiousity's sake.
There are other foods to watch with gastroparesis. You might want to try limiting your intake of fiber and fat. It varies for people, but the standards are less than 8g fiber and less than 24g fat per day. Combining these two rules, not eating gluten, eating frequently and eating probiotics have increased my health greatly. I do still have problems, because my gastroparesis is really bad, but it's at least better.