I was repairing a friends machine which already had a 3D screen before I replaced it with a new one. I don't know if there is anything else you will need to upgrade yours though. I can't see why. The only thing I remember being left in the rest of the assembly was the webcam. As long as the screen you get has all the proper cables you shouldn't need anything else. I could be wrong though.
If you get the OEM Alienware 3D panel it
should fit straight in your old LCD lid and you will never know the difference. Ebay should have the screens you need but there are probably plenty of parts stores in the US that you could contac toot. Very little of that way down here unfortunately.
The NVidia 3D Vision glasses are the ones that usually come when you order from Dell I believe.
No special tools are needed. Just some small screwdrivers and a prying tool. The bezel around the keyboard can be tricky the first time. Don't do what my friend just did and assume that it just clips out. There are screws holding it in! He snapped his. Take your time.
Use a second computer showing a teardown vid at the same time you're doing yours so you can take it step by step.
When you get to removing the back shell of the LCD, you may think it's not coming off (mine was on there pretty hard). I just put some soft material down, put the screen face down and put some firm but careful pressure down and forward on the back of the case.

I would just order the actually LCD panel first and see how you go. Like I said, I've never upgraded a screen, only replaced an exact one.
Good luck! It's really not that hard. Be very cautious of the cables and their connectors. Use a prying tool!
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This may help you get the bezel off
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Don't forget to remove the 5 screws that hold the bezel in though!! I think they are labelled with an 'I'