If you come to the conclusion that the hardware is defective you could as well try to move the camera module around in its socket (green arrow in the picture). Maybe this little movement helps against corroded contacts, if you stick a piece of a razor blade between socket and module.

And if you already have opened the device and have a razor blade: On the lower side of the little extra PCB with the camera flash leds and the micro SD card holder there are two contacts (red arrows) pressing to the shielding plate of the main PCB. I doubt, that they do anything else then giving extra GND level for the LEDs. Maybe they have corroded as well. With sliding the razor blade between the shield plate and the lower side of this little PCB you maybe polish them. When I hat to repair my USB port I removed this shielding and did not put it on later again, resulting in a black camera picture all the time.

And at last: Harden your USB port by scratching of the paint of the PCB to the left and the right of the USB port (blue arrows) and solder it to the copper apearing under the paint. Be very careful not to fill up the USB port inside. There are enough threads about this here.

Generally: Do nothing of the above if you don't want do risk damaging more of trash it completely.

Here is a post how to exchange the complete camera module:
http://wiki.maemo.org/N900_camera_sensor