I am just in the process of changing my seal on my 96 - 150. When the seal leaks it will drain out the drain hole in the bottom of the housing. Some special tools may be required. The cover with the alternator will come off relatively easy, then the main center bolt holding the flywheel must come out, it is a right hand thread. The bolt may take some force to remove, I took mine to a shop where the guy used a 600 ft lb air impact. The bolt is not torqued more than 30 lbs but it seems to grow in there, that is your first challenge. The second challenge is to remove the flywheel, a special puller is used that threads in to the same hole the bolt came out of and presses against the crankshaft with some force ie light tap with hammer on the puller to dislodge the flywheel from the tapered shaft. When flywheel and starter chain sprocket are removed the oil seal is visible and easy to remove. I made a small slide hammer to remove it. I made a wood dowel on my lathe the same OD as the seal with the center drilled out to reinsert the seal.