Would changing a digital lens (CCD, CMOS ??) improve the image quality on a camera ?

I have a cheap dashcam which has average image quality, you can see whats happening but you can't make out number plates if the vehicle is moving - even pulling up behind a car at traffic lights the plates are still difficult to make out.

I've got a couple of old digital cameras and wondered if I swap the lens with one of those (it's just two wires) whether the image would improve.

Is the lens irrelevant and the quality all to do with software and how the image is processed within the camera, is the lens on a 5 megapixel camera the same as one on a 1 megapixel one ?

The lens isn't CMOS/CCD, that's the sensor.

The lens is important but the sensor is probably tiny on the dash which is causing the problem.

Ah, the sensor, thats what I was thinking of.
As I suspected if the sensor isn't up to the job changing the lens won't make a difference.

No, you'd need to change the sensor. This is most easily achieved by buying a new camera.