Wondering if I can tackle this one myself? Just unbolt the lower unit and r&r the rubber impeller, right? Bolt unit back on, new oil, and go boatin'! Needs a special little doodad tool - comes in a kit in Overton's? Scale of 1-10, easy, too hard, or just pay to have it done? Gonna void my extended warranty if I do it myself? What do you all do?