MRI Tomorrow- What to expect?

I'm 17 by the way, and have never had an MRI before. I had a CT scan about two weeks ago, which showed the CM, and I was scheduled for an MRI for tomorrow before my appt. with neurosurgeon on October 13th. I have very severe symptoms, ex. excruciating chronic migraines, numbness in fingers/toes, cognitive impairment, ect.

What should I expect from the MRI? From what I know, it's a spinal MRI, but do they do more? How long does it take to receive the results from it?
Also, what is the probability that my neurosurgeon will suggest surgery on me? I have symptoms getting progressively worse, I haven't found pain medicine (besides narcotics) that help, and I've had to had to leave my senior year of high school because I'm in too much pain to go to school. Do you think he'll decide to operate?
Thank you so much!

I have had a good number of MRI's and they aren't too terrible. Really, really noisy and boring. The biggest issue is laying still. It's hard, especially if you are in pain.