You most definitely want the factory service manuals for this (or any) car. Benz (and also the partsShop) sell a CD set with all the manuals on it. Also you can find it on ebay fairly often.
If you prefer paper manuals, they too are available from the same sources. There are several: 2 volume chassis manuals, engine manual (specific to your engine), climate control, electrical troubleshooting and transmission service. The tranny book is the only one NOT on the CDs.
There are 10 CDs available for the 107, 114, 115, 123, 124, 126 & 201 chassis (some are pairs). There are 10 CDs available for the 90s (current) models, but they are not detailed service discs, they just have technical training material.
What was the question again? Oh, yeah. You need the vacuum circuit. It's in the books (or the CD).