A couple years ago I changed the brake pads on my old truck, so I changed the fluid on my wife's car at the same time. Took her car in for her "free" service at the dealer a week later. They called her and told her that her cabin air filter was filthy and needed changing and her brake fluid was burnt and needed changing. Couple hundred dollars worth of service costs.
Well... fluid was brand new, so I knew that was bunk. The cabin air filter requires the removal of her glovebox, which was full of stuff and they obviously didn't remove to check.
I don't trust them to do anything other than follow the manufacturers maintenance schedule. Even then, I don't really trust them, but if they screw it up, they are the one's fixing it under warranty anyways. Anything that the DEALER recommends is pure profit.