littlebuddie,
My guess would be that the 100 mile drive was long enough to allow oil to leak or mist through onto the disc. If it is the disc, and it has been blasted with oil, your thoughts on the R&R are correct. I think the "cooking" routine would only apply to incidental fingerprints or other items encountered during a installation.
Make sure your trip didn't seal the fate of a marginal motor mount, or loosen on up, as this can sort of mimic a chattering disc. Good luck.
Stuart
