Richmond 40 gal water heater from 2003 gurgles loudly when refilling, is that normal

I'm not sure what you mean by "gurgles when refilling." If you mean that it is making noise when heating the water, that is usually a sign that sediment has built up in the bottom of the tank. This results in the surface of the tank bottom to overheat and the sound you hear is the water flashing to steam. This usually results in tank failure as the glass lining will crack an the tank will rust out. If it's not too late you could drain and flush the tank to try to remove the sediment but if has hardened to a solid mass it won't come out.