Make sure you aren't stingy with the anti-sieze on the new one, so this won't happen next time. I feel for you; this happened to me. Spent 3 days total to replace all 4 brakes. Overnight WD-40 didn't help. A torch did, to a degree. What worked best was hitting the rotor on the edge (where the cooling vents are). Still took a bunch of pounding and a bunch more swearing.
