Service records from dealer or MBUSA

Dealer that sold my '91 300E claims that their service records only go back 5 years. I'm trying to determine what exactly was done approximately back in '94 when a cracked block or head was replaced and the bill was $5k. (previous owner, mother, doesn't remember) I suspect I might have another cracked block and of course am ready to ***** loudly if this is the second time it has happened.

Is the 5 year claim that the dealer claimed (Intercontinental Motors in Houston) true? Does MBUSA keep a centralized service record database where I could get repair records on my 300E such as this major repair?

TIA!