You may have a bad connection in the dome or the bulb may be shot.
Unscrew the dome & check the terminals & screws for corrosion, then check the black plastic screw blocks in the roof to make sure they're not busted.
A "Mustang" dome light is always an option too. Pretty easy to install.
I have plug-in led's that fit all different types of domes & I have led panels for even more light... but it sounds like you're kinda a do it yourself person, so I'd say to do a little experimenting with some pcb's & led's to see what you come up with.