I have seen a thread about returning a phone to Nokia for a USB repair eventually being done under warranty, do a search, you may get some more pointers.
There is also a video on youtube of someone taking the N900 apart.
Good luck, just stick to your guns, it was not fit for purpose so should be exchamged/repaired under warranty.
It was from the beginning a small grey dot on the screen when I first got my N900.
I emailed Nokia about the dot and they told me to take it to a Nokia service center.
Last week I was in the audience of a tv-show and I got my N900 with me.
It was -15 degrees Celsius outside and when I got into the tv-studio it was about 30 degrees Celsius. The LCD-screen on my N900 cracked exactly where the grey dot was on my screen. I guess the temperature difference made it crack.
Now I'm worried how the Nokia service center will deal with it. Think it's hard to get it repaired under warranty now when it's cracked.
In response to your inquiry, the screen of the Nokia N900 is considered as a spare part for the phone, which can only be replaced at a Nokia Care Point. Therefore, I recommend that you take your phone together with your proof of purchase to your nearest Nokia Care Point. However, replacing parts is not within warranty guidelines. Thus, there will be a minimal charge for the replacement and services.
The contact details of your nearest Nokia Care Point can be found at the weblink below:
