i recently had my cambelt changes and drove 300miles since but the yellow engine warning light is on,i went to a vw stealership and my mate put the diagnostic machine on it,it read camshaft speed sensor,or timing too advanced,the timing is set up ok,does anyone know if changing the camshaft sensor is a big job and how much these sensors are,also is it ok to drive with this on,surely it will only use a little more fuel?