Buy the factory manual
I just sold my 1998 Johnson Sailmaster 8 hp outboard for $700 because two strokes are illegal for use in Lake Tahoe. My model was exactly the same one that you have now. It came with either a 4 amp alternator OR the electric starter, but not both.I'd be curious to know what the dealer does to "winterize" your outboard? Lets see: Hose off the motor with fresh water; check the water pump impeller (he'd probably automatically replace it); drain the fuel from the carburetor; maybe even change the lower drive gear oil, and check for any obvious problems. That's about it! You can do that yourself in less than one hour. You can even change your spark plugs if you want to, even if it's unnecessary to do so. You do carry a couple of spare plugs on board, don't you? When placing the outboard into operation again in a few months, use double the oil in that first tank of NEW fuel.The head gasket....why that? Is there a problem? Do you do a precautionary engine rebuild or head gasket change on your automobile? If your dealer wants to do precautionary repairs he must be one hell of a salesman. If the engine isn't knocking, has compression, runs without power loss, and generally operates normally....leave it alone. You can hear the knocking...you can feel the compression when you pull start it....and you know how it runs. If it gets out-of-tune, no big deal. It just won't quit immediately. You'll notice a decrease in performance first, but then with two strokes it's usually just a spark plug change that's rquired.Everything I mentioned is something easy to do. Get the manual and save your money.*Use anti-seize compound on the spark plug threads. It can be purchased at any auto supply store.