Don't sweat the MRI. Take a few vitamin A (Advil) an hour before your MRI appointment, it'll reduce swelling and take the pain down a notch while you're lying motionless in the MRI machine... and ditto on the ear plugs, use 'em.
And as far as the surgery goes, sounds like you have no choice, so make the best of it. Be religious about your physical therapy afterwards, and don't try to come back before you're ready... augering is frowned upon by your superiors and us taxpayers
Do it right, and you'll probably be back in the air within 6-8 weeks, so the sooner you can get the surgery, the sooner you'll get back in the air.
Good luck! The only other advice I can give is, if they give you the option to have a CPM machine (continous passive motion) immediately after the surgery, USE IT! I studied Orthopaedic Biomechanics at Stanford, and moving a joint is the quickest and best road to recovery.
I rode a stationary bike trainer the day after my arthroscopic knee surgery, and I was walking the following day... gingerly