I have Medicare with Physicians Mutual as a supplement plan. There was no problem getting coverage for the tests and the procedure at Stanford. I do not know anything about Medicare Advantage except I believe it is more restrictive as to facility.
There are many posts on the forum in reference to insurance -- use the search function at the top of the forum to find the threads.
If you hae any questions about Medicare, please let me know and I will try to help you out.