Biggest thing that will slow you down is the possibility of breaking bolts. One nice thing about doing the work yourself is you have the time to go at your own pace and you can replace every single bolt and washer as you go. There are intake gasket kits available from the vendors. You'll probably find more things to do while you go inside. Probably want to remove the Y-pipe and get the under side of it milled flat. Replace all the water and heater hoses in the Vee and along the back of the engine. New hot water valve. Replace all vacuum lines. Maybe cap and rotor, plug wires, etc.
If all you want to do is ask a shop to strictly replace the water pump and nothing else "while you're in there", then one thing that can go wrong is if they replace the o-ring under the fuel distributor while rebuilding the intake system. That o-ring has a role in setting the vertical height of the fuel distributor in relation to the roller on the air meter see-saw. It will be necessary to set the CO again if that o-ring is replaced. That might throw the tech for a loop if he can't get the car started when he's done.
Note that it's not necessary to remove the FD since you can take it out along with the entire air meter system as a unit.
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