I was hit by an airbag 10yrs ago resulting in tmj. I have tried everything from splints to arthrocentesis. The MRI shows both joints are damaged & displaced & the lower jaw bone is now flat. Surgery is scheduled. Is this my best option?

Depends. Probably. Depends on the surgeon, and the surgery. Open surgery or artlhroscopic. Your surgeon should have vast experience with TMJ surgery Arthroscopic surgery much less invasive. Can be indicated even in a case like yours. Are you also being managed by a TMJ non-surgical specialist? You should be. Good luck.
May be part of sol'n. If you cannot resolve the pain with conservative means, then surgery may be an options. If your joints require surgery this will change how the teeth fit together. Surgery will be followed with a healing phase and during this time find the best functional jaw position. Treatments may be necessary to have the teeth support this new position if the bite is different than before surgery.
Probably so. It sounds as if you have tried allrevesible options. Good luck with your surgery!
Probably. Surgery is always the last resort. If all the other therapies have been exhausted and you are miserable daily, then try surgery. Make sure the surgeon is very very experienced and will move you into physical therapy during the post surgical phase.
Oral Surgeon. This is best left for a board certified oral surgeon to answer; however, it sounds like you have exhausted all other non-surgical options...And it's been 10-years. This issue will not "just go away". Especially with the MRI result, it sounds like surgery may be an alternative. Do you homework, get a good omfs, and listen to their advice. Also, no good doc will be upset about a 2nd opinion!