We changed our domicile to Florida with SBI mail service at the start of this year. In addition to passports, they required other items (like mail and proof of FL insurance) to issue our DLs.
Maybe I missed it, but I did not see any mention of registering your rv in FL. For full timers, RV is registered before DL's are issued. Then they use the your rv license plate for the address on the DL.
Since we did the whole bit at once, I am not sure what you will need if registering car before getting Florida DL's; check the websites carefully. Also be careful of legalities. If I recall correctly, you are supposed to register vehicles within 10 days of becoming FL residents and get DL's within 30 days.
Thankfully, we have not needed to see doctors since we we changed domiciles. Hubby is on Medicare. I bought a high deductable plan from Humana. Not great out of network coverage, so I hope not to need care on the road. If you do not yet qualify for Medicare and are able to find non-medicare plans with good nationwide coverage, please post the info.