Hi Dampman!
Insurance is available. There are a number of companies that will write you a policy for being here all year. IMIS is the one we use and highly recommend them see
IMIS Home Page
Also, buying a boat in Mexico is not all that difficult. Some paperwork hoops that the dealer would typically have handled for you via their "Paperman" (Ships agent).
While we haven't personally bought or sold a boat in Mexico, we've helped former owners sell theirs buy shooting a video to put up on the dealers website.
Regards,
Bill
Currently just North of Puerto Vallarta.