Unless you are convinced you need one exactly like the one you have (to preserve originality); then you are in luck. Replacement Microwave/Convection combos, or just Microwaves are relatively inexpensive, lots to choose from and available all over the place, with warranties in multiple sizes.
There usually is a modest mystery to get the old one out but once you figure that out (if I can you can) then the remainder is easy. Mine was held in by a back brace and screws on the top which were accessible through the cabinet over the Microwave. I think this is pretty standard. Once the screws are out it just tilts down and then you lift it off the brace in back.
1994 is not exactly vintage so the quest to preserve the look, if that is what you are after may take another thinking through. Otherwise have at it.
I do all my own stunts
03 Dolphin LX 6355, Workhorse W22, 8.1 vortec, 04 CR-V, Blue Ox, Brake Pro----Norm, Barb and
Doc(He's a PhD)