I highly recommend disabling your factory alarm when doing this. My 190 has other issues, so mine was already turned off at the relay box. I've heard that the car does not like to be started without the lock cylinder in, and will activate the horn/headlight alarm when done, and disconnecting the battery is the only way to kill it. Similarly, screwdriver starting sometimes trips something in my electrics, and disconnecting and reconnecting the battery is the only way to get power again to the car.

PM or ask here for questions.

Cheers