Here's some info from my mechanic friend.
I haven't found anything on the web.
[...]
My mechanic friend in Ohio says according to a CD he has: The going rate for R&R of a water pump on a 1993 Sentra car (not the minivan-thing) is 2.9 hours + maybe 1/2 hour for diagnostics is all it should take. His information says $78 for an Original Equipment water pump. It could add up to $400 depending on their hourly rate and what type of pump they'll use.
It sounds very easy to do according to his information:
Drain radiator, drain block
Remove belts
Remove pump
Use RTV sealant to glue the water pump in so it doesn't leak
Replace belts, install coolant, check for leaks.
Of course, he can't see how easy it is to get ratchets, etc., in there....
It sounds as if you allow plenty of time it should be doable if you've got the tools. HTH. Good luck!
Cheers,
Scott.
