How much is it to replace a PCM? Dealer says it's loosing memory.

What is your question?

We seemed to be setting of the Anti-theft system with trying to start the car. We couldn't tap the starter. If we wait long enough, a day or more, it will eventually start but then the engine light is on. Midas couldn't figure it out. Took it to the dealer, he's saying the PCM is loosing memory and needs to be replaced. He said it isn't the keys. I'm wondering what this is going to cost and if I have to have the dealer do the work.