It’s starting to sound like in order to save $200 on getting a key, he’s going to rip out and replace half the car. 
I think he should either bite the bullet and pony up money for a new key . . . or just bring the entire car to the dealer and let them figure it out
I’ve seen plenty of situations where the owner spends a lot of money by taking the shotgun approach, it doesn’t work, now he heads to the dealer and he’s irate
well this isnt a guess or anything if you change the ignition on a car you need the matching ecu and steering lock and its not hard to replace so i wouldnt really be spending that much money and lol its 2 parts which is all under the steering wheel. this i know would work but i was just seeing from my original post that if i could make it a little easier (which i cant)
I really think you need to take this car to the dealer . . . because you do NOT know what you’re talking about
The electronic ignition switch IS a module . . . if you replace it, you don’t need to also replace other modules
And you can change the steering lock and/or electronic ignition switch independent of each other
No offense intended . . . but you’ve demonstrated that you aren’t terribly knowledgeable about matters concerning the electronic ignition switch, steering lock and keys, in regards to this particular vehicle
Sometimes the smartest thing you can do is acknowledge you’re in over your head, and it’s better left to the pros, who in this case will probably wind up being the dealer
well no actually you might not know either in that case because you said that you just put the key in it will self program but ive already talked to the dealer and they have to program it themselves so im not sure you if thinking about the same type of mercedes cause thats not how you program this cars key. thanks anyways for the replies
good luck
anyways, I truly hope you aren’t out a lot of money by the time this problem is resolved
and I also truly hope you don’t spend a lot of money on unnecessary parts