This page shows what the deal is and the tabs I need to get at and remove. I hacked a good piece off of one of them with a pair of pliers, but I didn't get enough of it - I need to get the case off and get in there with a rotary tool (like a Dremel).
Update: Adam at The 2nd Last Gamestore offered to perform the surgery for me, and the next day I came in and he did it all right in front of me. Now I can play the Super Famicom games I brought with me from Japan (with prices between $3 and $7 they were too inexpensive to resist picking up). My Super Nintendo is getting old and glitchy, but it still plays Super Mario Kart, Star Fox, Street Fighter II Turbo (learning combos is hard work!), Super Mario World, Donkey Kong Country II... does the Super Game Boy work? Yes. I had it at Mike's place the other night and it wouldn't play his imported copies of Final Fantasy IV and V, which was disappointing - I'm now convinced that it's my system and not the cartridges, so I probably need a new or working used SNES - I'll keep my eyes open. There are clones out there like the FC Twin, but I'd much rather have the Real Deal™ - I've seen one in action, and it seems they can be kind of glitchy, perhaps due to the fact that they use systems-on-a-chip instead of the original parts.