Well...for half the year in the Bahamas and half in the bay you can expect to pay 1000-1500 bucks for insurance in a 35ft. recent vintage boat like the Catalina you spoke of.
I encourage you to pursue your ambitions as you will easily learn what you need with some diligence and practice. I second the vote on Beth Leonards book as a wonderful guide. For single handing, I think a good autopilot, furling mainsail and big honking anchor and windlass are "must haves" in a larger boat.
As for costs...if you anchor out you can live very cheaply...and if you go to marinas then you can spend a whole lot of money. Many people seem to cruise on betweeen 10 and 20K per year living pretty frugally and only going into marinas occasionally. The big hits our budget seems to take seem to occur when things break on the boat AND we have to make use of marinas for repairs. I''ve heard it said that you need to allow 10% of the value of a boat for annual maintenance and repairs...that seems a bit high to me but you certainly will need to plan for some emergencies and general maintenance. Good luck with your plans...GB