My .02 If the engine is that bad, send it back. I'd bet they send you a new one. They admitted that they screwed up (make sure you put that e-mail or a copy of the letter in the shipping box with the engine). I know it bites to be out of an engine for three weeks, but if someone at your club that does not the experience with the engine could screw it up even worst if they try to fix it. Unless I heard it, I couldn't tell you. You might take the back plate off and see if everything is still connected. It sounds to me like either a bearing has been spun or the connecting rod is bent. Sometimes just hangin out the field asking questions and observing is as good as flying.

Good Luck