Hey-
First, let me say good luck to ya with the outcome on your tests.
As far as the plate in your neck, it's likely to be titanium not stainless steel. Either way, it's ok to have an MRI. Orthopedic implants are safe in an MRI environment- I can't come up with any that are unsafe and I've been doing MRI for 20+ years. If the MRI can provide a definitive diagnosis, let 'em go ahead with it.
If you want to check out a sight by the guru on MR saftey,
www.mrisafety.com is the sight to go to. Frank Shellock has been teaching MRI safety since God made dirt and is viewed as the DUDE on the subject.
Good luck again
Bob