I'm about to install an Autopage RS850 alarm and I want to unhook the factory alarm. Is this possible without causing a problem?

It would help to know what year and model you're working on here.

Generally speaking, the factory alarm only arms itself if the car is locked in a certain manner (e.g. pressing the inside lock while the driver'* door is open, or locking it from outside with the key, or pressing the Lock button on the remote). I'm not aware that any part of the factory alarm would interfere with the Autopage unit. Does Autopage have any warnings about that?

To answer your direct question, I don't know how you would unhook the factory alarm, since it'* rather closely coupled to the keyless entry system, but on the other hand, I'm not sure that you would need to do so anyway.

I don't know if the Autopage alarm includes a keyless-entry feature, but if so, and it'* properly installed, it should be able to disarm the factory alarm when it unlocks the car.

That makes 2 of us

Sorry about that but I thought my signature would give a hint. It'* a 93 SSEi.