Drained my lower unit this weekend and found a little bit of water in the gearcase. I'm assuming that I need to replace the prop shaft seal. I have the O&M book for my outboard but I think it makes it sound harder than it really is. Is this something I can replace myself or would it be advisable to take it into a marina....It sounded like there may be a couple special tool needed to make the job alot easier.....The motor is a 2000 Johnson 150..... Thanks for the input fellas.