Definitely use your own car, you won't regret it.
I've done 3 weekend schools that were Porsche club schools. I used my wife's EVO for all of them and had a blast. You won't be going fast enough your first time out to break anything suspension wise so I wouldn't think twice about it. It is hardest on the tires. You will wear them down towards the end once you figure out what you're doing. It isn't even that bad on the brakes because they're going to make you break pretty early and you won't be heating them up too bad.