is there any way to unlock a 98GM radio w/theif lock without the code?

Answer 1

1st you have to know how to unlock the radio, this will be listed in the owners manual. Don't have that, just find someone with a simular car and kindly ask to take a look in their manual.
2nd When GM installed the radios they usually stuck a small while label in the glovebox with 3-4 digits printed on it. This is the theft code from the factory. Ocassionally a dealer will remove this during dealer prep and put the label in your owners manual.
Most good dealers will unlock the radio, with code available for little or no charge. If the code is not available you will have to goto a dealer and prove ownership and they can unlock the radio for you. This normally includes removing the radio so they can pull the serial number off it.