ooooooooh, I fell sorry for ya pal. Your fastest fix (that I know of) is to simply import the files (in real time) into a sequencer, like cakewalk or power trax pro -whatever....and then change all the channels, and program changes to match the standards. I don't think there is anything "out of the box" that could decipher what sound you "wanted" to use in the GM map. Like Karen & Rich said:
" It's gonna take some time, this time!"