Well that really depends on you. Do you have experience with disassembling electronics? Do you have that delicate touch required for dealing with small parts? I have been 'fixing' things for years so it was no biggie for me.

There is a video or two on youtube about N900 disassembly, look them up. You need to:

1. Undo 4 screws to detach the screen, both visible behind the battery cover.

2. You then need to detach the screen ribbon.

3. You then 'unhook' the screen from the keyboard (this is the 3rd most fiddly bit).

4. At this point the screen is now separated from the N900.

5. At this point I would re-attach the ribbon (the second most fiddly part of the job) and extremely very carefully power the N900 up (be careful, the screen will be flopping around). Test to see if the problem is resolved. If not, power down and detach the ribbon again.

6. You then remove the 6 screws holding the slider to the screen.
The screen can now come apart, the final connection is in the middle. De-attach this ribbon then re-attach it (the absolutely most fiddly part of the job).

7. Re-assemble and cross you fingers.

All the connectors just 'pop' together with a subtle muffled click, don't force them, when they are lined up they go together with little force.

Obviously make sure you are doing this at a good/table bench, you have a decent set of jewelers screwdrivers, a nice bright lamp and are very patient.

I can disassemble and re-assemble my screen in about 15 minutes, a first timer id say easy 30-40 minutes.