Brake light switch problem

First off I have a 2000 Escalade that every few weeks I was having a small problem shifting out of park. After a few seconds it was normal agian. EVery time I went to a shop they couldnt find anything. Finally it happened in front of the mechanic and I was told it's the brake light switch. Can anyone tell me where it is? Or if I can change it myslef?

Im sick of turning the key a little shifting into neutral, starting the car than shifting into drive. This is not normal for a truck that I paid 49K for


Any help is apreciated!