I like the way you think. I would have no problem having a hissy fit in the showroom, I'd even do it for less than 96% certainty.
Here is the receipt they gave me. They actually charged half of what they initially told me the labor charge would be... but doubled the cost of parts.
When I asked them about the parts cost, they said they don't make those "after market" parts for my car and I had to get the GM parts.

 

A dealership will always use OEM parts before any other.

All they did was fiddle with parts markup check the parts on Google if you want to see where a bunch of profit is made. For example, one of those ac Delco parts cost you $300+, available on Amazon for $100. Their list price was already twice that. Etc.

Do you see a charge for oil or a filter? I don't. They must have recycled yours.
No charge for dexcool either. Explains why reservoir not topped off.

Other possibly is they just shaved the labor to match your quote because they had to by law.
I doubt that job is listed for 1.5 hours.

Is it maintaining the coolant level?

 

I think you're second possibility is accurate... both mechanics estimates included $300 for labor for the water pump job, no extra for the timing belt since they were in the area anyway.
If it's not snowing too badly this morning, I plan on going to see them and ask them about he coolant and oil. Will also return a tool that was left on the passenger floorboard.
Wondering... was it necessary to drain the oil for the job they did? I didn't ask them to change the oil and I don't recall them saying they would. Besides, why would they change the oil and not filters?

I'll get back to you when I have some news.

 

I'm thinking they had to disassemble enough stuff to get to the timing area that they might have needed to drain it. If a timing CHAIN, that needs constant lubrication.
Unless it is a timing belt in oil bath (which I don't believe was ever used on the L cars (Andy?)), they wouldn't need to do it for that reason. if they were replacing the front oil seal under the timing cover, yes, but they didn't.

As for the tool, please post a picture of it before returning it. You did not steal it, it was implicitly given to you by someone as a gift.(JOKING) I would give it back but do so personally to the mechanic it belongs to, which is CP ??Ask them who.
Andy -- I have ALWAYS returned left-behind tools to mechanics -- it's unethical not to Each mechanic buys their own tools -- it is not up to the dealership to do so.

---->>Actually, before you go, clean off the outside of the reservoir. Some have a FULL COLD and a FULL HOT mark, and yours may actually be at the FULL Cold mark, which is not necessarily at the halfway point.
Should have thought of that ages ago. My bad.<-----

Check owner's manual, verify it is Dexcool, etc go to autozone, get 50/50 compatible coolant, and refill yourself on a cold engine.IF IT IS NOT AT THE FULL COLD Mark. Andy would know if it has one. MAke sure the cap is tight when done.

Maybe they did not have to change the oil.

I keep referencing Andy as he is the resident L car specialist. I make it a point not to blindly answer questions I do not know the answer to --I may inadvertently do so but it is not my intent. We try to work as a team here on this forum because no one person knows everything about every model. Andy (02 LW300) rebuilds L car engines.

Good luck. Check the reservoir for the cold full and hot full before going and looking clueless. My bad.

Let us know the outcome, please.

 

"Check the reservoir for the cold full and hot full before going and looking clueless. "
LoL too late for that!

I decided to take the helpless ignorant posture when talking to the mechanic, rather than being confrontational.
I asked him if he could show me how to check te oil properly, since I checked it yesterday and I thought it might be low. I also told him the coolant was about 3" low again.
When he popped the hood - low and behold - the coolant was right up there where it should be! Duh? Did I look stupid, or what? lol
He said that happens, but didn't explain it like you did. As for the oil, I asked him if they changed the oil and if so, did they also replace the filters. He looked at my receipt and determined that they only added oil.
I was satisfied with his answers.
Finally, I showed him the tool. He said he had seen it, but it wasn't his. Must belong to the mechanic at the other place. Going by there tomorrow.
I have no idea what kind of tool it was - 3/4 of it looked like a screwdriver, but the business end resembled a crow bar... kind of a two-prong fork.

Still... if it took them so long to determine there was a problem with the water pump... and the coolant lever fluctuates normally, I wonder if I just paid a whole bunch of money for something that didn't need fixing?

 

Your initial post said you had to keep topping off the coolant every three to 4 days. After everything else being fixed, it really does sound like the water pump was a quite reasonable diagnosis.
If you do NOT have to add more coolant every four days anymore, then the repair done WAS necessary, as was the replacement of the other parts.

Coolant expands with temperature as the car warms up. Getting to the halfway mark sounds about right. Look in the owner's manual and see what the coolant reservoir markings are.

The key is --- if you do not have coolant vanishing every 4 days, then the water pump was indeed in need of replacement.

Plus the timing belt was prob original, and likely needed changing -- see owner's manual for maintenance interval for that. Prob 100K but don't quote me. Andy is the L car expert.

 

Thanks, I feel better about it now. I'll keep an eye on the coolant.