Personally, I think 4 hours is a bit steep for a competent mech.
Have a look at the schematic diagram here and decide if you want to tackle it yourself.
Since the pump is easily accessible and once the radiator fluid is drained down, it might be easier than you think. The only snag might be pushing out the roller bearing (item 5). You could get the unit off and take it, with your kit, to your man and ask kindly if they'll put it together. A chargeable hour tops.
https://www.ajsutton.co.uk/genuinepa...ter-pump?uID=0