Wow, I don't know how I missed this thread. Sorry for the 3 year late response!!!
Anyways, I was in the process of revisiting this project and searched around the forums to see if anyone else has done anything like this yet. So here I am.

Better late than never, yeah?!?
So on the circuit board there is only one surface mount diode (SMD) that is labeled LED1. The only button that would be illuminated would be the AUTO window button. Also it is so dim because it is being covered by the silicone/rubber piece that you can see in pic 2 & 3 where I had trimmed it back.
The window LOCK and door Lock buttons has no light source. If you look at the last picture, I had to cut a hole behind the door lock just to get light through it (only to find out later that there wasn't even a light source).

Images are hosted at my blog.
I'm working on adding in three 3mm white or orange LED's (not sure if I want to go all white or all orange yet) between the circuit board and switches. They have to be perfectly aligned with the holes to get even/proper light without making them look faded or inconsistent with each other.
I'll update with more pictures as I finalize the project and put together a how-to.