Re: Changing water pump
You probably want to order a manual to help walk you through this, but you can also look at diagrams
HERE. You'll need to click the drop down to "Stern Drive" and then choose yours.
The connectors for the shift wires are on the port side (left if you're facing the front of the boat) of the engine, just in front of the intermediate housing. Those will have to feed all the way through the upper gear case. I suppose it's possible to do the work with them connected, but I'd be terrified that I'd lose control of the lower and break 'em.
Shouldn't need any seal kits for what you're doing (besides the new plate for the impeller housing.