Unfortunately that's not necessarily the case for examples from the 90's. Remote keys have been problematic for a while, although Mercedes are currently looking into a new solution/supplier. ISTR a member here recently found M119 throttle bodies were NLA from Bosch for the moment. Certain ASR sensors are not currently available. These sort of things are a showstopper if you can't find/engineer a way around it or turn up a good used part to keep you going.
That legendary unshakeable parts supply has arguably had some wobbles lately