OK regarding the bulb/cover. The best way of trying to get this off is to get a set of pipe grips and a hot rag. Cover the glass cover with the hot rag and then gently back and forth it until it releases. Do this carefully so that the whole assembly does not start to go round and break the power cables. If this doesnt work then its a case of replacing the lamp assembly in total.
Regarding the rivet problem, could you let me have a picture and description of the problem so that I can try and identify a solution. -- Ian