Bienvenue à TF. And congratulations on your 19 years with your GB. Obviously she's a keeper!
If I'm reading you correctly, this is some sort of lamp that illuminates the breaker panel so you can see the labels, etc. I added a photo below of this type of lamp near the helm of a 1991 GB 32. An arrow points to it. Maybe this is what you have?
I wonder, do you know if you had a short circuit, or if maybe the lamp or wires just heated up (resistance). That could start a fire or melt without even tripping a breaker.
At any rate, this seems like a great spot for an LED bulb. Much cooler temperature.
If you want to re-use the fixture (or maybe use a new fixture of the same style), I have found Marine Beam to be a great place to get LED replacement bulbs (to replace old incandescent bulbs). They are good quality plus they help you identify which bulb will work as a replacement.
If you need further help, they actually answer the phone and do not say "Dometic, we have taken over nearly every small company, can we generically help you?"
Nope, you are likely to get Jeff on the line and he will be happy to talk intelligently about his products.
Here is a link directly to their replacement bulb page:
They also make entire fixtures, although I don't see one that matches the style I showed on the 1991 GB.
Other brands or solutions may work too of course.