Oldsmobile Alero overheating

No, not for that price. Is not talking about the timing but the timing belt. Replacement of that belt and the water pump are recommended, but find another mechanic to give you another estimate. The cost should be less than half of that.

Was the car all right before you took it in except for the thermastat and water pump was put in. I would think it was vapor locked. What that means is there is air in the circulation system keeping the water from circulating.
Check when cold. Take radiator cap off. Then start the car have someone watch the temperature guage. With the water in the radiator a little low on top of the fins watch to see when it starts to circulated. You can also feel the top hose. When it get warm then the thermstat has opened. That way you know the thermastat and pump are working. After a couple of times of starting and warmeing up. The vapor lock usually goes away.
Iif it still overheats take it back to the garage and ask to have the thermastat checked out.

Take the thermostat out run the engine-is it overheating w/o it. Do you hear any boiling @ the radiator.

Best way to catch this is Block chek and pressure test method.