its a pretty straight forward job.
remove the belt, then unbolt fan and pulley, drain and catch coolant, remove the hoses, remove the radiator, then unbolt the water pump. Some bolts that go into the water jacket tend to be rusted stuck after 36 years; take extra care not to break off any bolts. If you do, its your luck with the EZout (not recommendable) or a trip to the machinist.
For changing the water pump, you´ll need a new pump, bolts, paper gasket that comes with it and a suitable sealant, like RTV engine silicone (permatex or master, or polyurethane-based blue hylomar).
Test fit the pump and check for binding, I had two pumps whose impellers didn´t clear and hit the cylinder. Possible solutions: either pressing the impeller closer to the pump housing, or by using two gaskets.
Also, compare your new bolts to the old ones, they should be of same length.
Get the mating surfaces real clean, then apply a thin film of sealant, put on the gasket, apply another thin film of sealant, then put on the new pump. Put a light coat of teflon sealer on the bolt threads (ARP thread sealer, but any non-hardening RTV will work as well) Snug the bolts tight by hand, then torque them down slowly in a criss-cross-fashion, checking for any binding of the pump occasionally.
While you´re at it, how´s the thermostat?
Depending on the conditions, you may want to flush the cooling system.
Acetic acid (30%) worked well for me, then flush with ground dishwasher detergent tabs. Those are caustic and will neutralize what remains of the acid.
