My first major repair I think ! after an airmast replacement !

You mean the Serp belt?? This is not a repair, its normal maint. This part is a consumable

call it drive belt ... when you cant steer anymore ???

You can't steer ... or you lost your power steering?? I would think you lost your power steering and replacing that belt is FAR from a "major repair"

If you did not replace it till it broke you are not doing any preventive maint. Suggest you rethink your vehicle maint program if you even have one. And, its not a drive belt. It powers numerous accessories in addition to the power steering. Its called a Sepintine Belt.

last one was done at 60k and everything check out fine .... change the airmast filter .... then off to hawaii .... called MB Hawaii they told me that around $200 but also gave a scenario about the pulley ???