Please help. Buying a hummer h1 tomorrow

[Blackwidow]

I'm buying. A hummer h1 tomorrow and the dealer just called me and told me that the compresser, tensioner, and belt need to be replaced for the ac. It's a 1999 wagon. He told me he will take 500 of the price because that's how much a new compressed, tensioner and belt will cost installed. Is this true? I don't want to get ripped off on my first h1. Thanks in andvance for your help