I LED'd all the interior cabin lights on a DIY basis several years ago. At the time, manufactured LED conversions were still new, not all that great for lumen output, and outrageously expensive as all new technologies tend to be.
Now, for just about every type of old style bulb fitting type/size, you can find an LED "drop-in". The Store section of this website has many types. Or do an Internet search. Cost is very much improved.
You do not need to replace the whole fixture. For my 1980 Cherubini Hunter, the interior the bulb type for the seven dome lights is festoon. LED "bulbs" are made now that will just snap into the fitting.
When I did my conversion, I actually removed the dome fixtures and brought them home to give them a thorough cleaning; and I also cleaned up the tarnish that had developed on the switch interfaces over 25 years. The plastic lenses came out bright and shiny and clear. All-in-all the dome fixtures held up very well through the years.