I'm replacing the pump seal and shaft right now too... same problem. Parts are ordered.
- remove filler cap under the tank, undo brass allan plug on pump, spew coolant all over the place til you get the pan positioned right
- remove hose clamps and hoses
- remove 3 allan bolts holding the pump on
- remove circlip holding it all together
- with the brass plug out (also acts a bushing for end of the pump shaft) stick a screwdriver or something less sharp in the hole to hold the impeller while you turn the pump shaft to unthread it from the impeller. (left hand thread, mine was only finger tight)
- pull the shaft out, then you can use a screwdriver or equivalent to gently pry out the seal. Note the way its put in (backwards to a normal case seal)
Mine was missing a thrust washer inside the pump, which may be the reason its leaking now. (used bike)
Mike