Car will not start

Well first you are going to need to get the correct ignition switch and keys so the alarm system can detect the key. Next you will need a dealer to program in the new keys so the system will work. The fobs will also need to be replaced and programmed into the system. At the moment the car thinks it has been stolen and has shut off the fuel and ignition. Until it sees the correct security information from the key and fob it will stay off.

Without the factory scan tool, access to the factory programming information and the dealership codes it isn't possible to make it work. Those are the simple facts. There is no way to bypass the system, it reads the information from the key, if that information doesn't match the information programmed into the ECU, BCM, and the instrument panels processor it won't run. Period.
You may not like it but that is the way Mercedes designed the system.

No you don't understand. That vehicle has systems on it that require the specific scan tools and programming that ONLY the Mercedes dealers have access to. Unlike many other makes Mercedes doesn't allow access to their data by non authorized shops. So Bobs shop on the corner can't get the programming info to work on them.
Same thing is true with other makes as well, Rolls Royce, Bugatti, Ferrari, BMW, Skoda and others don't allow access. You might get regular service info like how to change the fluids but most of it isn't available to anyone who isn't a dealer.
Are most dealers overpriced? - That depends on how you look at it, add up the cost to buy the dealership from the company, cost of the building, taxes, astronomical insurance rates, all of the tools and equipment they are required to buy and the normal business overhead on top of that. Then you add up the labor costs for the technicians and the insurance and it is quite a price tag. On average a shop pays the techs under $25 an hour for the top techs, The rest pays the bills.

They are still my last resort as a service/repair shop unless it is for something that cannot be done anywhere else.

You have the same issue with Mercedes as farmers do with John Deere. Both make their equipment so that you need their special software and tools to be able to work on the electronics. The factory specific scan tool for that car runs $18,000.00 plus about $1,000.00 per year for updates. Want programming access as well, add $400.00 a month. This is something that ALL of the companies are trying to do, they are using the DMCA to say that the software is proprietary and that they cannot let other people into it because then the software could be altered to make emissions or safety systems fail and the company would be held liable.

All of the companies now integrate the security systems, keys or fobs. Programming them requires access to the factory data, without it you can easily brick the computer modules and turn a nice car into a car that goes to the salvage yard because it is so expensive to repair or worse you cannot get the parts. Many of the modules used are a one time unit, you program them for one vehicle and that's it, they cannot be programmed again. Mercedes isn't alone in that.
As a different example take a look online for Chrysler TIPM issues. That is the smart fuse box, it controls just about every electrical item on the vehicle. Each has to be programmed to match the VIN and options the vehicle has. They are failing at a rate faster than the company can get new ones made! Currently they are on a 3 month back-order. These are something that was designed and implemented by Mercedes when they owned the company.

Personally I consider every vehicle out there as a pile of bolts and parts that will need repair sooner or later. The problem these days is getting the parts and info to do that.

You think I'm being an ass for sending you to a dealer. The facts are that they are the only ones who have the access these days to actually do the repair you need.

The only way around that system would be to gut out the electronics that operate the engine, transmission, instrument panel and entertainment as each has a part in the security system. That is intended to make it harder to steal or sell parts if the car is stolen. It also makes them much harder to repair without all the access needed.

There is NO loophole. That is why they are a pain to work on when they break. On the older cars there were resistors you could add or you could fake the signal from the transponders. Those methods just don't work because now it isn't a single point system. The key/fob is not queried only at initial start like the old systems. It is now queried repeatedly and using multiple signals to determine if it is valid to the vehicle.
That is why thieves don't even bother to break in anymore unless it's to steal items left out in the open. They will instead just tow the cars they want and strip off the parts.
Sorry but that is the truth with todays vehicles.

Heck even the Journey I have out front takes a rolling code transponder style FOBIK and has two spots for an actual key, one emergency lock in the drivers door and the glove box. No key needed for any of the rest of it. When the wife bought it I ordered two new FOBIKs and programmed them myself. That was because my scan tools can do that. I have 6 different ones in the shop these days, from a cheap code puller that I grab to just see what a code is quick, to a couple OTC units, A couple Snap-On units, a newer Autel and a Launch that I'm testing out. I also know what it's like to lose tools, a crook broke into my shop a few years ago and grabbed tools and 2 scan tools plus trashed the place.

However it's your vehicle, Get all the info you can and see what happens.