300e voltage draw

I have a 1990 300e. its been parked in my garage for a year and a half. all of a sudden it is killing the battery. what i have noticed is the radio is not powering up any more and of course the power antena dosn't go up either. could it be one of the relays in the fuse box or is it the factory radio ( can't imagen its the radio). the relays i am talking about are cream color and semi transparent and about a inch and a quarter square. would they have something to do with it? i sure could use some help with this one...

is the battery still good?
does the alternator put out enough power?