forget the cam belt, the M112 has a chain usually good for at least 200,000 miles or so.
Water pump you can DIY, about a 2 on a 1-5 difficulty scale.
Expect low end on a water pump around $90, high end (if you go to a dealer ) around $350-$500.
also coolant flush with 50/50 distilled water and Zerex G05 - around $25
may as well do a new serpentine belt while you are in there, around $30-$40

also change the oil, Mobil1 0w40, 8 quarts and a Mann fleece filter, around $60 if you get the oil on sale at Wally World ( I just paid $22 per 5 qt jug )

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