i did it last year. it was a lot of fun. very tiring. i thought that because i did a lot of track days, that i would have no problem with the conditioning. i never realized how much i could relax when not actually racing.
it was intimidating from the stand point that we were one of the few teams that had no experts onboard. however, we still had a lot of fun. and you can really learn a lot from getting passed by fast experts. i'm sure they hated us, buut we had a blast.