I would just winterize it myself.

Fuel stabilizer can be bought at any home depot or boat store.
Put that in no matter what. Gas doesnt stay fresh just because you
start the engine for every so often. Good to move it around a bit but
it doesnt solve the problem.

When winterizing you should change the oil and fuel filter. Oil
can be acidic and damage the engine. Drain and replace.
As for the draining the block... If it gets cold enough it can
crack the block. I have had a few friends that did their own work
incorrectly and forgot to go the block too. Byebye engine.

You can do the job right yourself and save some money while doing it.
Its not all that hard to do, just take some time. Look over this
newsgroup to get a nice complete checklist of what to do when
winterizing it.

Tom