+1 on doing it yourself. I purchased my first boat last March and the whole maintenance process can be intimidating. Pick up a service manual for your drivetrain and start reading. I purchased a Seloc for 2001-2013 Mercruisers for $18 on Amazon. In addition, there are some very good videos on YouTube (take each one with a grain of salt, as there are some not-so-good ones as well).
With basic knowledge and tools, I've been able to change the oil, winterize, remove the stern drive, replace seals on the upper unit, and the water impeller in the lower. Seriously, dig in to it yourself if you can. The things you will learn are invaluable, and the money you will save can be spent on more stuff for the boat.
Personally, after I winterized my 3.0 last season I can't believe people would pay to have it done. On the 3.0, it's only 2 drain plugs.