No way to know the cost of repair without getting inside the set. Make
sure if you take it into a Philips Authorized service that if you
decline the estimate that they are willing to keep the set so you wont
also have the cost of disposal of the hazardous waste.

Given the symptoms you currently described, it really sounds like the
buttons have gotton liquid contamination inside the tv set. It is at
least worth having checked out, even if you plan on keeping it as a
second tv set in the other room.