There are a couple articles that detail the backlight replacement bulbs (three for your year IIRC) and the procedure to replace them.
I did a quick search and found this link for you: http://www.corvetteradios.com/
I know that this site has an instruction link and photos on it somewhere.
Bottom line, you can get inexpensive replacements from Radio Shack for under $3 and, with a litlle time, you'll be good as new.
Ahhhhh, I finally found the good repair article by Harofreak00:
the radio light fix 00+