How old is the non-failed strut?
I once replaced only one strut on the rear of my 500E (they cost $400+ each), since it had only 44k miles on it at the time. No problem there. However, I'm inclined to think you need to do both fronts, unless the good one's fairly recent
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car