Having the twin of that motor, yes the oil does tend to make a bit of a mess. Tiling it is what i have found works, about halfway up. And yes, it is the large bolt halfway down on the left side (standing behind the motor looking at it). Stop at the Merc dealer and get the socket for the oil filter, made by Merc. The filter is extremely difficult to get off if not using the socket. In your manual (if you had it) it would tell you to run 20w40 oil as the regular oil in the motor. If you need more info, or a scan of the pertinent parts of the manual, pm me and I will scan it for you when I am at home.
Trevor