Take it to another shop. Look at the link Pizza guy provided. It is the same part I recommended in my previous. There you will see the parts required for a changing the conductor plate. That service manager is full of himself; You do not need to drain and put new fluid in the transmission just to clear the codes. I really doubt they would use the correct fluid which really could cause you to replace the transmission. The 722.6 Mercedes transmission is very particular about the fluid. GET your car out of there!!
If you get the codes cleared you may just be okay. GET those codes cleared before any other work. If you can drive the car after that you will be fine. IF the codes reset then you must replace the conductor plate. It is at that time you will be flushing and replacing transmission fluid. BE CERTAIN THEY USE THE CORRECT FLUID! Read my previous post carefully. The only other acceptable fluid is Shell ATF 134.
I was asking where the care was kept because leafs often fall and clog those drains under the windshield cowl. Non the less, It is a highly recommended to pull that cowl off and be certain the drains all are clear and working well. Does your siren sound when you push the red PANIC button on your FOB? You need to hold the panic button down for about three seconds to get the siren to sound. IF the siren doesn't sound you can either replace it while you have the cowl off, or disconnect the siren electric connector. It is best to have it out of the cars electric system if it is not working, It is easier to get the windshield wipers off if you use a small gear puller. I cant get them off simple by hand.