Quick message...

At the very least, you will need this glass (or something like it):
http://www.ebay.com.au/itm/New-Touch...item43b39107e7
When looking for this glass, do not forget that microphone should be included!
http://img.auctiva.com/imgdata/1/2/8...68_o.jpg?nc=83

Also, when you will be replacing the glass, there is high probability that the plastic-and-metal frame around the glass will snap. Either detach-reattach the frame really carefully, or get two new parts. One is plastic-inner (0253126) and another is metal-outer (0253144). Just search "Nokia N900 0253144" and "Nokia N900 0253126" and you will find them. Like here:
http://www.ebay.com/itm/NOKIA-N900-A...-/331284555444
http://www.ebay.com/itm/NOKIA-N900-A...item4d23e8a02f
I do not know why mixtronics currently gives no pictures, but I have bought these parts from this store just recently. Everything was fine.

And take care when dissembling-assembling the device! Do not force anything, or you will destroy the heads of the screws, or something else. I could post you new M1.4x2.8 screws (there are six of them within the display part of N900), but shipping across the world is too much.

There are service manuals available.
http://wiki.maemo.org/N900_Hardware_Hacking#Resources

Best wishes.
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Per aspera ad astra...