Tires: Valve stem problem on 2004 Explorer, 2004 ford explorers, pep boys

Question
A few months ago, I noticed a missing cap on one of my valve stems. I purchased some nickel plated caps and replaced them all. This week, I noticed the pressure looked low on one of my tires and tried to remove the cap. It was frozen and when I applied some force the stem broke. I found that all the caps were the same and could not be removed. I went to a VIP/PEP boys and they would not work on it and said to take it to the dealer.

The dealer said that they all needed to be replaced and because of the pressure monitoring system it would cost $766!!

Any suggestions?

Thank you.

Answer
Carl,

If 2004 Ford Explorers have TPMS's - and while I am not sure that is the case, VIP/PepBoy's response seems to indicate that is true - then you have a major problem.  You might want to go to another Ford dealer or perhaps a different tire dealer and see if you can get a better price.