As a fellow combat veteran, thank you for your service. Also, very lucky to have been asked to do a med fet play session!
I would find out if there is a particular type of scene she is looking for. Some possible routes with this is a more straight forward physical exam (never a bad option!), a specific kink related medical scene/roleplay (ex. psych ward, OR, etc., though the possibilities here are endless to be honest), or if there are other types of play that incorporate medical kink into it that she is looking for.
I would find out if there are particular things, types of exams, or procedures that she specifically needs or desires. Some people are really into the speculum exam/vaginal procedures, rectal/prostate exam, auscultation, or enemas, to name a few. I would also find out if there are exams or procedures that she does not want or has limits on as to how extensive or invasive they are.
When it comes to medical play, a simplistic view of the flavor of play tends to be a spectrum between "Totally professional" approach that emulates a real physical exam, to the very "sexually or kink focused" approach; many fall somewhere in between. There is also the flavors of the "stern physician approach", along with the "gentle and caring" approach. I would try to find out where along these axis' she falls.
You mentioned BDSM, so it may help to ask if there are elements of pain that she is looking for and how much is enough or too much.
I will end on consent stuff. You need to ask what her hard limits are in terms of the play or procedures, and have a safety word in place. You should also address level of sexual contact. Medical play for many is highly sexual, but that doesn't mean that your patient or partner wants certain sexual acts performed, or anything performed at all for that matter. Likewise, you can also set limits on what you are comfortable doing and what things are off limits to you.
Equipment is pretty easy to get on ebay or amazon if you don't have it, so based on your conversations with your play partner you can figure out what you actually need to buy and what you can skip on.
I hope that gives you some direction to go with your conversations!