Clock in Grand Marquis

I have a 1993 Grand Marquis.
Since Sunday, my clock is din, not really visible.
At night, I can barely make out enough to tell that it is actually
still
keeping time - it just doesn't display brightly enough to see.

When it first went out, it would go out, come back again, go out, come
back,
and this repeated intermittently for a day or two. Then it went out
totally.

Any ideas what the problem is? From the research I've done, I'm
guessing there's a
light bulb in there that burnt out. If this correct, how can I
replace the bulb?