Re: Carburetor Rebuilds
Carbs are certainly a DIY type of job for anyone with a little mechanical ability. No special tools required but a service manual will come in handy when it comes time to set the float levels etc. This is a crucial setting. The parts price you were quoted is way out of line.
As for resealing the LU, that is a much more involved job if you intend to replace all the seals. That being said, there is no reason to replace all the seals. A simple pressure test of the lower unit will reveal the leaking seal, and only that seal needs to be replaced. Depending on which seal is leaking you may or may not require special tooling.
Being that this motor is new to you, I would recommend that you replace the waterpump impeller at the very least. Once the pump assy is taken apart you may find that other components will need to be replaced as well.