I've had the 4 hour radioactive egg test done 3 times now.(I have Scleroderma). It really is no big deal, just boring. Take a good book with you. You will eat the eggs and toast, get scanned, then wait an hour, scanned again, etc.
I am actually having a gastric pacemaker implanted this week. So, there are meds and procedures out there for gastroparesis. Good luck on your test!