How do I change the water pump

Simon, how many miles or KM on your engine now, when was the timing belt last changed, in my place, the entire job gets done at the same time, a full timing belt kit comes with a water pump, oil seals, all bearings, tensioner and everything else needed in a Master kit. You should not go much over 80K miles on a timing belt and less if it has oil leaking on it.

Why pay labor, for example, if you change one major item that requires all this labor just to have the other major item go bad in a month or so, happens all the time, new timing belt puts more tension on the water pump bearing so it starts to leak requiring the full timing belt job to come off again to change the water pump soon after, that requires 30 minutes more labor to complete along with the timing belt job. Do the job right the first time if you are going to put your name/reputation on the line and save labor/cash for the customer.

Since this is a DIY job, do yourself a favor and do everything once and its good for another 80K of normal use, less heavy duty use, more light duty use. Make %#*@ sure you got the correct alignment marks to reinstall the timing belt. Mark the belt to the pulleys if you keep the same belt and the direction its turning now.