Transport 98 radio theftlock system

I just recently bought a transport 98 and looking into my "haynes" manual (I don't have the owner's manual) noticed that if I need to do some repairs I need to disconnect the negative cable of the battery, but in the manual says once this happen the theftlock system of my radio (AM-FM-CD) will turn it off permanently at less I enter my LOC code (also I dont' have it).
I have a theftlock LED in the radio, and never goes on.
There is a way to know if the theflock is disabled before the negative cable is disconnected?, Or I need to go to the dealer?, or just the LED off is the signal that the system is disabled?
Thanks for your help.

The owners manual gives a variety of security options. My guess is that if the light ain't ON your fine.

Don't worry about the LOC code. I had to reset the power slide door, and you guessed it, the radio "loc'd" on me. Quick trip to the dealer and all is fine and now I have the master code for the radio. Most dealerships will do this for free. It only requires them to extract a code from the radio, call head office and viola your master code.

Ok, thanks for the advice