MagD Switch removal
First, pry off the rubber cover on the switch. It just fits in a groove in the top of the switch and should just pop off. Then take the long end of a 5/64" allen wrench and insert it into the hole in the center of the switch. The allen screw is clear on the opposite side of the switch at the bottom of the hole. Just loosen the screw a couple of turns. Make sure the switch button is depressed and the switch should just slide out the bottom of the light. Sometimes they stick a little, so when that happens, I put the wrench in hole and use the leverage to rock the switch side-to-side to break it loose.
Once you have the switch removed, you can use the same 5/64" wrench to remove the screw holding the bulb post in. You will then need to pull out the negative ground screw nut and the long tab that sticks clear up into the bulb post. You may also want to remove the switch internals to prevent fouling it with "sawdust", it just pulls out. Then you can chop off the bulb post and just leave the opearating parts of the switch. You will also need to cut the the negative ground screw tab to length. You want to leave enough to solder to, but not so much that you risk it contacting the positive connector in the middle of the switch.
Here's my alternative to soldering the wires directly to the switch:
Modding a MagD switch with screw down terminals for wires