Blazer stuck in PARK

My 1997 Chevy Blazer is stuck in park. I know about the shifter
interlock - but I questioned if it was that because my brake lights
work and when I push the lever on the shifter I hear a clicking under
the dash? Can the lights work and switch be half bad. Can something in
the shifter itself be bad? I guess I'll replace it tonight if I know
how to ask for the part? Any other problems it could be? Or is this
probably it. It is on level ground and seems to rock back and an forth
freely an inch or so.

Thanks for any help.
Shawn