Just for info, probably many of us know this already.

The LCD on the N900 is separate from the resistive grid / screen - you can buy each part separately so if your touch screen fails there is a decent chance you can restore functionality with a new one. The touch screen costs around $40 USD so I guess no harm in trying :-)

To replace this part is a relatively painless operation, just google for an N900 disassembly video and follow along as far as you need to go.