HELP!!! disable factory alarm on 84 500sel!!

[brockley]

First time posting here and I just bought my car last weekend. I have used the search function and everything I have read tells me to look under the false plastic firewall in the passenger footwell and disconnect a cable from a box marked Becker Electronics or something like that. When I remove the plastic panel, there is nothing behind it, only the real firewall. Connected to the back of the plastic panel is a light gray box with one connector connected to it about 1.5 inches long. According to the label on this box, it has something to do with the built in car-phone and its connected transponder. I need to know where I can disable the alarm because it goes off 10 minutes after locking the door or if I try to unlock it via the passenger door. I found what looked like an aftermarket hood in the engine bay and a disconnected it but the factory alarm still went off. I need to disconnect this tonight so I can lock my car at school tomorrow without it going off.

I am also trying to figure out what my car came with since there was no instruction manual with the car. I also don't know if it is a Euro or US model. The temperature control is in Centigrade (Celsius).

Any help on either of these would be greatly appreciated as soon as you can respond.

Thanks.
Brett