Dom Perignon

[Novice]

I'm going to have the opportunity to buy a case of Dom Perignon at an "unbelievable" price. It is something that someone has had in a warehouse for a while. I don't have the vintage yet. I'm concerned it may be "too old" and not in good shape if it has been in a less than optimum storage area. How old is too old for Dom, how vulnerable is it to heat, and how do I find out what is a good price? Thanks.