Hi,
While you are in there, it probably will only take an additional 30 minutes to replace the water pump. If you have to replace the pump 3 years from now, it will require removing the shroud, fan clutch, and all that stuff, to get to the 6- 8 bolts that hold on the water pump.
I know this because my brother in laws Dodge 360" engine required a water pump, and then about a month later the engine died. It turned out to be a bad timing chain! Then engine already had about 175,000 miles on it, and it was 'take everything off again, and replace the timing chain' At least the 360" engine, it was 'easy' to get to the timing chain while in the engine bay. ..
How many miles are on your RV?
I would not consider replacing the water pump on my 1997 460" engine with 55,000 miles on it. I have been using a water filter since it was new, so the coolant has been mineral free, and the water pump bearings and seal should be clean as they where when new - on my motorhome. . .
I had to replace a idler pulley on my 1995 Windstar van. I think that the dealership wanted something like $100 for one, but the junkyard had one for about $10. That one worked fine until I sold the van a couple of years later.
Good luck,
Fred.