A good place to start would be phoning your RV insurance company to ensure you have the required insurance such as Mexico liability. Your insurance company should be able to provide you with that.
Secondly, you may want to to check your medical insurance and find out how you policy and how the clinics and hospitals works inside Mexico.
The answers to your remaining question(s) can be found on the usa.gov website under the link --->
Entry/Exit Requirements for U.S. CitizensIt talks about tourist cards, passports and vehicle requirements etc...
Happy Trails enjoy your stay!