Has anyone been to Mayo, and dealt with Medicare reimbursement?

Hi, I have an appointment at Mayo in Rochester, MN, in late February. I'm hoping to get a diagnosis one way or the other - though it sure seems like EM to me. But my insurance is Medicare, with (so-called) full supplemental insurance (I haven't had to test if it's for real yet). Mayo doesn't accept Medicare if I'm not hospitalized, which I won't be, though they say they will file it for me.

My fear is Medicare will reject the claim, or if accepted, pay very little of it. And that my Supplemental insurance won't cover the difference. I can't afford to pay for everything myself, which I imagine could be a LOT! It will be enough to get to MN from New Mexico, and pay for a motel and food.

Has anyone had any experience with any of this? I am on the fence about whether I can really make the appointment, or should I cancel, because of expenses.

I've read on this site that Mayo can diagnose, but doesn't offer much help afterward, so I'm not expecting that. I just want an "official" (can one argue with Mayo?) diagnosis one way or the other. But am wondering if I should just call the whole thing off. Any ideas?

Thanks so much!