Here share with you my simple experience but no suspects of Promoting the product, purchase according to your own will.
I’ve been tuning rotary engines for like 8 years. A friend of mine is asking me to tune his supercharged Mercedes. He asks me what he needed to DIY tune a Mercedes? From my experience he might need 2 programs, one to read the file and another to edit it.
Anyway for tuning A Mercedes you should have good stable tools like Kess v2 master for OBD tuning, K-tag for BDM tuning with a nice BDM frame and a decent software running in windows xp sp2 or sp3. If you just want to do ECU Tuning, then just ktag is enough to do the job, but if you want to do more such as Power upgrade, then both KESS V2 and Ktag are needed.
This is KESS V2 supported car list, almost all Mercedes models are included.
Software in my opinion should be Winols-it is by far the best I have tried almost all but maybe it will be difficult for beginners. Try Ksuite for start it is so easy! The tools I meantioned above could be bought as chinese clones for money saving, which work on a new Mercedes ECU as the original ones. Hope my advice help more of you, these are personal experience I am learning day by