I feel your pain!
I did this a few months ago, and it was the single most difficult mod I have done. The lighter drove me nuts. I spent two hours trying to get it to open, you have to push down a clip or something with a mini screwdriver or similar (I used a knife).
I will give you some advice, don't replace your currently lighter unless you really need to. I would switch mine back if it wasn't so difficult, because nothing fits the new one very well. This is perhaps the first time I have overmodded my Boxster.
