Heed the advice of the mechanic and the instructor. If you haven't done it already, go to the second thread on this Message Board, click on the first message, and read the paragraph which starts "If you are considering buying a Skymaster....". That paragraph has a link to a page that addresses exactly your questions and then a summary of what's in the link. Incidentally, I'm an aerospace/mechanical engineer (MS, Caltech) on my second Skymaster.
A more current discussion on maintenance costs may be found at
http://www.337skymaster.com/messages...?t=2703&page=2. This thread is on Skymaster Valuation, but on this second page the discussion meandered into operating and maintenance costs, and members gave the actual costs they have been incurring. The discussion on these costs starts with the third message on that page (edasmus' actual operating costs) and ends with Paul Sharp's message further down that same page. Two things are worth noting. First, there is a wide range of costs, with some members citing Annuals (including parts) costing $25,000 while others pay around $2,000. Second, there is a link on one of the messages to a separate page where members were asked by the then Administrator to share the costs of their Annuals. I caution you to read this material carefully, because some costs include engine/prop reserves while others don't, and "operating costs" may include fuel, hangar, insurance, etc.
Ernie Martin