Yes, there is an IDM-100 that has a very weird layout. I think its for some of the very first 94 powerstrokes. I've only come across 1 in the 10 or 20 I've modded so far. It still uses the same resistor, just located in a different spot is all. Its not hard to find, only bright baby blue one in there.
As for getting the cover off, I usually try to slice a razor knife all around the edge as best I can, then I get 3 or 4 of those little flat screwdrivers, and starting from the corner on the connector end, start working it under. Be careful about the plastic connector housing, as they can crack. And yes, try not to bend the crap out of the top cover plate. You want it as flat as possible to put back together.
I've got two IDM 120's in a box under my computer desk that I bought off ebay like 2 years ago. Just havnt got around to modding them yet.