I just went through a similar situation, did my first rebuild on a 1979 115hp. I think I spent $1500 in parts and boring all cylinders, they were mic'ed and all were out of round as Faztbullet mentioned they might be. I opted to rebuild since I already replaced the stator, trigger, and switchboxes (ADI ignition), which wasn't cheap and I love the TOP motors. I was lucky to find a blind borer who also had the merc piston installation tools - even with both of us wrangling it in, the dressed crank was a bear to get back into the block.
It is time consuming, and yeah a single sentence could equal hours of work for a novice. A factory service manual might be better than the Clymer when doing all this work. It also doesn't hurt to read ahead and get a feel for what's happening. Good luck!