I can only relate my experience on my car. I did not disconnect the battery.
When I removed my radio for the first time to clean the tape transport after following a lot of good instructions from forum members.
After reinstallation the Becker display had either "enter code" or 4 dashes. Forum members said it neded to be reset.

So I took it to the DEALER and the service writer guy pulled out his little box about the size of a eyeglass case took out this little tool and we slide the radio out about an inch. He asked me if theft was a problem. I asked him why, and he said that if we leave the anti-theft wire disconnected and he reset it then I could take the radio out anytime and not have to do the reset again. He reset it by pressing some little button on the side of the display something you can not get to unless the raido is not in tight.

Also remember that to get the radio out there is a BOLT that is only reachable by removing the glove box liner and then removing this bolt that goes through a metal tab and into the radio chassis.

Best of luck. J