First thing i would recommend getting is some good tools. If you want a window you are going to need to hack into the side panel and despite all the urges, your kitchen knife is not the tool here. I would recommend getting a Dremel tool; they make the cleanest cuts in my book. Also a file is a good investment for smoothing rough edges. That being said:
You have two options with getting an LCD screen. You can buy a kit, like the one posted earlier, or if you are feeling ambitious you can make your own with a little money and a trip to radio shack. Here is one example from another site, but ill let you look for more because computer modding goes way beyond what you have mentioned and I think it would be good for you do look around, you might find something else you want to do.
http://www.gideontech.com/guides/lcd/ this is one such example
As for the window mod, you can find the guide to those vary easily (almost every site has one) I will however make a suggestion. Practice before you go hacking on your computer. Find something that’s like the material of your computer case, draw some patterns and cut. You wouldn’t want to mess up on and have to buy a new side panel. The second is doing your prep work, the old carpenter’s rule of measure twice and cut once. Make sure you thoroughly clean the modded part before and after cutting one it, metal dust is bad. Any time you have to draw lines or something like that do it on an inside surface or with pencil that way you can easily cover any mistakes. I know this all seems like simple stuff but its something often overlooked. In the long run its worth it no mistakes make the mod you will be happy with.