Definitely a good idea to replace the impeller. Their easy to get at on that boat. Sitting in the spotter's seat, the impeller housing is practically right in front of you. If the old one still looks good, throw it in the glovebox to be used as a spare.
Skidim has them or your local inboard dealer. Assuming you have the TBI 350, I believe it's the Johnson 812.
Change the oil & filter at the very least. Theres also gear oil in the trans, but I'd just check it to make sure it's full & not cooked & let it be. Great deals on oil & filters at your local Napa auto parts store now days.
(Message edited by bill_airjunky on May 22, 2009)