If you want to find out the facts, talk to the actual tech, in person.
Ask who did the repairs, then when you get there, ask to speak with them to thank them for their help, then grille the shit out of the svc tech about what was actually performed step by step. If they throw up any bs about well hes on lunch, hes very busy, ie not letting you speak to the tech RED FLAG. if they let you speak to him and anything sounds different from what the svc advisor is saying RED FLAG. Watch for any eyes drifting, pupil dialation, fidgety, or anything that says that the service tech feels uncomfortable. Im a pretty good read on body language ymmv.
Then id request they give me a refund for the prior work done for all your trouble, trying to bs you into a $5000 bill and the FACT THEY PROBABLY EFFED UP YOUR VEHICLE IN A WAY THAT YOU MAY NOT BE ABLE SEE FOR A WHILE.
If they try to null on that, tell them something along the lines of, im going to go ahead and leave my vehicle here while i contact my attorney to see how to proceed under the consumer fraud protection act. This whole thing smells like cover yo asss.
AT A VERY MINIMUM THE LABOR FOR THE PRIOR WORK SHOULD BE REFUNDED. But personally, i would consider actually speaking to the your legal rep or the Atty general. and consider small claims court if they refuse to refund.
Dealers are required to have the competence to perform the repairs without negligence. Clearly, the were negligent in that one of their idiots got water in the engine during their process, and now they have Admitted to fault by repairing the additional work at no cost and by admission. Now as a result you have suffered a loss.
Heres a great link,
https://www.nolo.com/legal-encyclopedia/free-books/small-claims-book/chapter16-2.html