Take off the faceplate, remove all the batteries (especially the backup coin cell), unscrew the case, and pry it open. You're going to need a torx screwdriver for the case screws. Theres also clips holding the case together. Don't be too worried if you screw them up because they're redundant.
Unscrew the circuit board and pull off the RF shield. Be carefull because once you take the board out there will be nothing holding the buttons in.
As you can see in the picture, the screen is glued onto the PCB with a thick piece of aluminium between them. Now we have to remove the LCD screen and plate from the motherboard. This is tricky. You must be extremely careful, because the LCD is made from very fragile glass. It will chip or crack very easily. Also be careful not to cut or dislodge the ribbon cable. If either the screen or ribbon cable is broken, it cannot be fixed. There is no hope. You're calculator is dead. The end.
Begin by using a knife to pry the aluminium plate off of the motherboard. Be patient and take your time.
Now is a good time to cut your EL panel down to size. Lay the LCD on top of it and trace around it with a marker. I chose to have the leads going out the right side (facing the front of the screen). You can cut the EL panel with scissors. You might want to trim off some of the excess laminate on the side with the plug.
Once you cut it it will be small enough to be powered by the tiny inverter. Plug it in and test it. Save the extra bits for later.
Now we need to get the metal plate off of the screen. This is the most dangerous part of the project. Get some rubbing acohol and pour it into the holes in the back of the plate. This will help dissolve the adhesive holding it to the screen. I let the rubbing alcohol soak in overnite, topping it off as it evaporated, but this is probably overkill. Don't worry about it shorting out the electronics. Its not water. Just make sure everything is dry before you put the calculator back together.
Take one of those extra pieces of EL panel from earlier and start sliding it between the aluminium plate and the screen. Any other thin piece of plastic will also work. DO NOT USE A KNIFE or any other metal object. Add rubbing alcohol as you go to help dissolve the adhesive. Every now and then, pull out the seperator and clean off the glue.
Work your way around the perimeter and use more of the extra panel to keep things seperated. Luckily, the glue is only applied around the perimeter of the screen. Be very patient and do not use too much force. Be careful not to put too much stress on the ribbon cable as you work. Eventually you will be able to pull the plate completely off. Give a sigh of relief, because the hardest part is now over.
Now is a good time to test your LCD and make sure it still works. Load the batteries back into the back half of the case. Press the motherboard against the back half of the case so the battery connectors make contact. Use a screwdriver or some other metal object to short the pads of the ON button in the lower left of the PCB. You should see the screen come to life with the standard "RAM Cleared" message. Try pushing some other buttons to make sure the whole screen is working.
On the back of the LCD there is a reflector and a polarizer. This diagram shows the different layers.
The reflector is a thin foil sheet on back of the polarizer. It needs to be removed so the backlight can shine through. The polarizer is a thicker plastic sheet on the back of the LCD glass. I recommend replacing the polarizer as well because, if you're like me, you probably screwed it up in the previous step. Also the stock one isn't particularly transparent. Carefully peel both of them off the glass with your fingernail.
Take the new polarizer film and slide it behind the LCD. If you turn the polarizer one way, the screen will be transparrent. If you turn it the other way, the screen will be opaque. Behold the magic of polarized light!
Now you have the option of inverting the screen colors. You can have dark text on a light background (normal) or light text on a dark background. Choose which one you want and then test it by repeating step 8.
Once you have decided which way the polarizer should go, take it out and cut it down to the size of the LCD.
Assemble your LCD sandwich with the EL panel on the back, then the polarizer, then the glass. You can use some scotch tape around the edge to hold everything in place. I used some putty to stick the whole thing to the PCB, but you could also use some double sided tape and that stupid metal plate.