[patw]

Oddly enough, I couldn't find a procedure on how to do it after my running light filament burnt out. There's 2 filaments in the bulb (type 1157), found pretty much anywhere (got mine from a 24hr Walmart at 10:30pm).

Process is stupid easy and can be done without tools:

1) Pop passenger seat.
2) Pull up the strange black wire holders (made of some flexible metal). Pull the wires out so they're easy to work with.
3) Disconnect rear light (white connector, not the black one).
4) Twist the white plastic bulb housing sticking out of the back of the tail light unit until the tabs line up, and pull out. It was a bit stiff, so it didn't look like it would twist at first.
5) Remove old bulb, replace with new. Return things to original state.