Heater Box removal and retrofit

[hardyboy1704]

The Car: A 1977 300D.

The Problem: My servo (I think that is what's called) box is cracked and, thus, I have no temperature control.

The solution: A mercedes mechanic told me to just remove it and put a "valve" in its place. Ok, sounds easy, but where do I get the valve, how should it be setup, and what do you do with the vacuum lines that are just left hanging there?

Please advise or give me a link.

thx.

gabriel