This voids your warranty. So make sure you want it bad enough.
You will need to get some polarizing film to replace the existing polarizer. Best (cheapest and easiest to deal with) source I’ve found is Scientifics Online.
Update: The above link seems to no longer work, so I went looking for a reasonably priced source for linear polarizing film. I haven’t bought this stuff, but there’s a decent price at Edmund Optics for a few different sizes of flim.
Update again: Alert reader Phil points out a good source for polarizing film in small quantities: polarization.com
The metal bezel that holds the LCD onto the board needs to be removed. To do this, get needlenose pliers between the boards and twists the metal clips so that they are aligned with the slots in the board. There are six or eight of them, and they all need to be in line with their slots. Then the metal bezel can be removed (and polished, painted, etc.).
Take note of the orientation of the LCD glass! It makes contact with the PCB by means of a couple of flexible contact strips at the top and bottom edge, but once you remove it, you may not be able to determine the correct orientation. Maybe some masking tape on one end would help.
The polarizing film needs to be removed. It adheres pretty tightly to the LCD glass. You’ll need to get a sharp blade under one corner to start it. Once it’s started, pull it off by applying a very steady pressure in a plane parallel to the LCD glass–if you pull perpendicular to the LCD glass, you’ll quite possibly break the LCD. While you’re pulling, try hard not to disturb the contact strips at the top and bottom edges–you don’t want these to come off.
Then take your polarizing film (the new stuff you’re using for a replacement) and place it up against the LCD glass. Rotate it until you see the minimum light reflected from the LCD glass (i.e. it gets darkest). That’s the correct orientation for the polarizer if you want your LCD inverted.
Then cut your piece to size, cut it to fit inside the metal bezel since you can’t adhere it to the LCD. Replace the LCD glass on the board, making sure the orientation is correct and that there’s no crud between the board and contact strip. Replace the cover and twist the tabs back into place.
inverted, old-school style