2004 Ford Explorer Crank Pulley Problem

I have a 2004 Ford Explorer that was bought new from the dealer. It has 48k miles on it and just recently started making a loud screeching noise. Brought it a trusted mechanic (not the dealer as I have had horrible experiences with them from day one) and was told that the crank pulley was put on backwards. The mechanid showed me and explained showing that the serpentine belt was not able to ride along the propoerly grooved and smooth edges because the crank pulley had been put on backwards. He told me to take it up with Ford, which I did. Ford corporate customer service was of absolutely no help at all and basically directed me to the dealer.  The dealer directed me back to them...crazy!  The dealership told me very rudely that there was no way the crank pulley could have been put on backwards. 2 weeks after my car totally died in a busy intersection and I had it towed to teh closest auto garage. They told me after putting it on diagnosis that the pcs (mainframe computer system) needed to be reflashed and that only Ford could do that. Ford dealership told them that they would have to charge me again for teh diagnosis fee ($95) even though this other mechanic had already done it. Upon Ford dealer looking at it they call me to say that the crank pulley has now fallen apart completely and needs to be replaced...a $650 charge. ?! And that they can't check the pcs or anything else until they replace the crank pulley entirely. The whole things just sounds wierd and unexplained to me as well as fishy especially after having 2 other mechanics look at the car. Has anyone else experienced this or similar problems? What is your opinion as to who to believe here? And does anyone out there know if it is in fact possible for them to have put the crank pulley on backwards when teh car was manufactured?