I just went through this whole issue on a 2004 314ce i just picked up. The thin plastic cover that goes over the screws is attached with some type of contact cement. It can be carefully pried off with a knife after popping off the battery cover. You can remove the battery compartment by pulling it out, and unsnapping the phone type plug. However, to replace the unit, you will probably need to remove the stings, and re-plug it from the inside - tricky but do-able. good luck!