yes i would becuase you know soon as you get all back together and put a few hundred miles on it you have to go thru that whole senerio all over again .but if your handy and don't mind doing it again you could leave it alone you might get 10kor more out of it but first check it to see if there is any play in the bearings.
I would be inclined to say yes, replace the water pump while everything else is "disassemble all over the place" - depending on how much the replacement pump costs and how major an operation it is to pull the rad/hoses etc again.
I know on my smallblock gasser, water pumps are inexpensive and plentiful. Not sure if the word "diesel" equates to a ton more $$$ for a water pump. If so, you might want to leave it until it has to be done.
Same goes for how big a job it is to tear down again, if it's fairly simple which I believe it should be on a Chevy truck you can always do it later, if it's a major undertaking do it now and save yourself a bunch of aggravation.