As far as the MRI, the information I can find is confilicting. Some say it's good to have done, others say it won't help. While it won't help with nerve damage, it will show if there is anything in the tunnel like a tumor or ganglion. Your doctor will also see this if he opens you up.
The information on whether or not to jump for surgery is conflicting. Some say, only a last resort - others say that it's important to catch this early on.
What you do is ultimately up to you...but I'd consider the following...
Is your doctor a podiatrist or an orthapedic surgeon? If a podiatrist, I would be very reluctant to go ahead with surgery befoe consulting a foot and ankle surgeon. Not that I have anything against podiatrists, but a second opinion is warranted any time you consider surgery for anything.
Have you tried everything else? Anti-inflammitories, rest, ice orthotics, acupuncture?
Does your doctor feel that delay will cause further problems? If there's no rush - don't rush...but if he/she feels it will make things worse that might change everything.
What does the doctor think the outcome of the surgery will be? Has he/she done this surgery a lot? What were the results?
TTS surgery outcome seems to depend on the cause. If the cause is something like a ganglion or varicose vein causing compression...the outcome is usually good (because the problem is removed).
If the problem is due to structure (flat feet) or systemic (from diabetes) the outcome is not so good...because the problem is still there.
i know these aren't answers, but hopefully it gives you some things to consider.....let me know what happens!