I just bought my 1st benz,a very fine looking 94 320e.The car didn't come with books and has 80k on it.I disconnected the battery for replacement and now need a code to turn on the radio.One dealer told me I need to get the radio serial # on the back of radio,and if i do that I'll change the whole radio which I don't want to do now.Any ideas on an easier way to get that code?