The water seal set is part number 19217-657-023, should check with your parts supplier to see if it's available.

you will need to pull the pump cover, which will require the replacement of the gasket. From there you will need to look at the shaft, bearings and oil seals to make sure they are still good (may need to replace some or all of these). The online parts manual shows a good exploded view of the pump and what parts to look for. The service manual outlines what to inspect for when serving the pump as well.

As for the power valve shaft. My guess is the previous mechanic had some technical difficulties with the reversed threads on the shaft and screwed it up pretty good. His solution was to simple weld the valve control arm to the shaft. Getting the valve out shouldnt be an issue if you can remove the bracket from the cylinder and pry the shaft out (its a press fit). But you will want to replace the entire setup once you remove it...
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Charles Gallant