Difference between Multitouch and non-multitouch parts?

[AlphaCentaury]

Hi,

I broke my x61t's screen a few weeks ago. It is a non-multitouch XGA G5 screen. So I'm now trying to find replacement parts.
My first problem is to find where to buy the parts and IBM asks for 900$ to repair it. I'm looking for parts all over the web but you're never sure that the digitizer is included... in fact, what is the digitizer?

I've found this video showing how to replace the screen, but I haven't heared anything about any digitizer and I'm not a native... Does his replacement screen a digitizer? Or is it a part he is using again?
http://www.vimeo.com/3933798

I'm thinking about to upgrade my x61 with an SXGA screen or with multitouch too. After having watched the video carrefully, I'd like to understand what parts are additional in a multitouch model. Is the protection plate different? As it is a capcitive technology (the protection plate doesn't play the role of a sensor), can I use the one I already have? I've found a used multitouch screen on ebay, right reference (13n7226) but the guy says it has a lot of "wear"... If he's speaking about the protection plate, and I can replace it with mine, it would be great.

Thank you for your help, I'm missing my poor tablet...