BMW 750il v12 HEADLIGHT PROBLEMS!!!!

I have a 1991 bmw 750il v12 and the headlights inadvertantly switch to high beams at random times.
I'm hoping its just a switch or a relay or something simple but knowing this bmw's complexity I'm probably not that lucky. Does anybody know of this problem and what it might be and how INCREDIBLY EXPENSIVE its most likely going to be. I just bought this vehical and I am wondering what "normal" problems are associated with these cars and what I can look foward to fixing in the future. HOW DO OTHERS RATE THESE BMW'S? DID I MAKE A GOOD CHOICE? ARE THEY HIGH MAINTENANCE?