There are several problems with this. Firstly, it is quite possible to screw your n900 by taking it apart - at least one actual electronic engineer by profession has had it fail due to the LCD cable not working afterwards. Secondly - the PCB has between six and eight layers - you absolutely cannot see where circuits are. Drilling through it is a really bad idea. Thirdly - you can get exactly matching USB connectors from digikey.com or mouser.com or ... for a couple of dollars. Fourthly - if you're not sure it's covered by warranty, ask first before soldering!