Mamiya 645 Super. Fix it or chuck it?

Anyone know the going rate to repair a stuck shutter on a Mamiya 645 Super. Apparently these things are the red-headed stepchild that Mamiya would like to forget about. On mine, the shutter cocks and makes a sound like it has been tripped but it doesn't open. The mirror also gets stuck in the open position on occasion. The camera was labeled in excellent condition when I bought it from KEH but of course none of this happened until the return period had expired. I already ordered a 645 Pro to replace it, but I'd like to repair the Super and use it as a backup if it is cost effective in the age of dirt cheap film bodies. Mamiya wants over $200 to fix a body, which is somewhat ridiculous given the market price for a used replacement. Any other places I might send it to?

P.S. Supposedy there is a certain range of 645 Super serial numbers which are even more trouble-prone than most. Any idea of what they are?