50hrs is the reccomended change interval, so you're good there. The oil does not look new coming out at 50hrs, doesn't look like I drained it out of my diesel or anything, but it's definately used.
Change the trans oil as well if you're not sure when it was last changed.
I cleaned and oiled the K&N air filter once on my '96 just because and never touched it again. Haven't touched the 06, looks like new still. IMO, unless you're boating in a dusty environment
, it stays clean almost indefinately.