Theftlock audio system

I would like to replace the intake manifold gasket on my 2002 malibu but I need to turn off the theftlock on the radio first. How do I find the code No. I need to turn off the lockout feature? I think it is part of the vin No. Any ideas? On this model they warn me not to unhook the negative battery led with this theftlock on. Help!!
Mr.gangle