97 S420 / DAS - ECU - DTCs / DRS?

I've read many posts in the group recently and would like to thank those that have supplied good info for the benefit of all.
Now onto the problem. My S420 with 120K was in to the dealer two
months ago and had multiple-multi-point checks with thumbs up all around. Two weeks later I decide to order another IR key. I bring the car in for key pick-up / programming. They bring the car out of the shop to me but when I go to use the new key it doesn't work. They bring it back in. It comes back out and seems to work but now the aftermarket security system doesn't chirp when activated. They can't seem to help with that as it's aftermarket.... I drive off.
Days later the Check Engine light comes on, then a day after that the ABS and ASR lights come on and don't go off. All three stay on after multiple short trips. I bring the car back.
I'm told the car has codes P0130, P0150, P0410 and P1584 and that the ME-SFI control unit has an internal fault. Must replace the ECU, O2S and stop lamp switch S9/1. I did my research and now know all about those codes and too much about ME-SFI but here is....
THE QUESTION - is it possible that they previsouly fried my ECU when programming the new key / DAS? Is it possible to dammage the ECU while working on the DAS? Any other ideas on why the ECU would suddenly tank?
Are they Dirty Rotten Scoundrels or have I just had a run of bad luck?
While waiting for the new ECU to come in (NOT CHEAP) I've driven the car almost 800 miles. All the MILs have remained off since leaving the dealer. Car seems to be running fine. I'm confused.
cheers mike b.
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