Dr. Inman isn't my surgeon but most of the St. V's surgeons require about the same thing. So..this is only a best guess and you'll learn much more on the 5th.
1. I don't know about the payment plan stuff but you could try going to
www.carecredit.com and see if you can get a credit card to cover it. Care Credit is for medical expenses. If Dr. Inman's office will work with Care Credit, you can get free financing for 12-18 months (depending on how they set it up) provided you pay it off in that allotted time. That is how I paid for my portion of plastics & my bridges.
2. A medically supervised diet is any medical doctor or dietician. Usually the insurance required fod journals from you and a copy of the doctors notes from when they saw you & discussed your diet with you. That can be an internist. It usually is not the WLS surgeon.
3. Any good WLS surgeon will require you to take supplements. If you don't, you are going to be one sick puppy. It will be a given that you will need to take (3) chewable multi-vitamins. I recommend the one a day chewable gummies for adults. WAY better than the chalky Flintstones. You'll also be required to do (3) chewable Calcium, B12 sublingual (or monthly injections), and B1. I would recommend you start doing Biotin at least 6 weeks prior to surgery. Many post-ops have issues with the condition of their hair & nails shortly after surgery. Biotin helps to lessen those. Post-op, you will also be required to drink protein drinks. It is the only way you are going to get in enough protein to support your body. Remember, you aren't going to be eating the food it is use to. I know you think you know your body now but trust me, your body changes post-op and it's needs changes rapidly. Follow as closely as you can to your surgeons post-op requirements. The better you do at this, the healthier your outcome will be.
Best of luck...