Weeping Water Pump and other opportunities.

Hi Folks,
I recently put my 81 KZ 1300 on the lift to adjust the valves. They were no big issue, the bike has only 7,000 miles on it. As I was putting the engine through a complete heat cycle, before I took it off the lift, it started weeping from the drain at the center front of the engine.
Unfortunately, I've been here before. Soon after I actually started riding this bike, years ago, it developed original leak. Which I repaired, perhaps in-artfully. 
At that time I noted that the water pump shaft was pretty well corroded, right up to the very lip of the oil seal. I replaced that seal and the mechanical seal as well but had my doubts about the whole effort because of the corrosion on the water pump shaft.
Any way : Here I go again.
I've purchased a water pump shaft but need to put together a complete lift of the gaskets and O rings I'll need. In addition to what ever machine work I'll need done. (I don't think my radial arm saw's up to it.)
Is a base gasket necessarily part of removing and reinstalling the head?
That'll be my first question.
The other opportunities include a steel idler gear. The nylon gear in this one shows significant wear.
TIA
Bill

You'll need a new head casket if you are replacing the cam chain idler gear with -say -- a Liska. The head has to come off. But the engine block doesn't need to be removed for either the gear replacement or the water shaft and seal . So you don't need a base casket .
As a note . I used Cruisin Image big bore kit, pistons, rings and his gasket set  probably 13 years ago . Still working as it should.
I bought two gasket sets from them about a month ago . Paid by Paypal on the Monday - had them by Friday . -shipped from Japan