i am not sure there is such a thing as rebuilt mpem. There is a guy on line here that can fix mpems that are blowing the 5amp fuse but I have never heard of a rebuilt one.
I also have 96 and realize how hard it is to get an mpem for your boat. I was looking in to this a few weeks back as I was trouble shooting and did not realize if I had a bad mpem or not. If it turned out to be a bad mpem then I was just going to go with the msd enhancer and wire it to bybasss the mpem. I could have got the entire thing with wiring harness and all for under $400.00, double that for oem mpem, if you can find one on ebay even. The msd part number is 4255. instructions for bypass of mpem for this is at;