Thanks to the three of you for the input and ideas. This is a rather simple birch cabinetry piece ( built to match the vintage in our early 1900s house). My husband can do wiring, and we have a basement so I am not worried about that. And, I still have the stain so that could be matched. One of the reasons I'd thought about this option rather than just sliding in a complete new unit was because I know that today's appliances do not seem to last as long as the older ones. (Mine are still functional but are looking a bit tacky and long in the tooth.) And, with an integrated unit like this if the microwave goes, the entire appliance is no longer any good. But, this is perhaps now sounding like it may be more bother than it is worth. Fiddling around to reconfigure the cabinetry I'd probably end up spending the same amount of money as just buying the more expensive replica unit. With two singles rather than one integrated set I'd get more options to choose from. But, frankly, I already have a nice, new Wolf range so this would be a secondary oven. And, to me, a microwave is a microwave is a microwave. I guess I'll have to do some more thinking the whole thing through. Thanks again for all the help.

We had a combo unit, and one did experience an early demise. We were a little annoyed with the extra expense of buying another combo unit however what we discovered is that would have been a deal compared to what actually happened. Nothing on the market at that time would fit the cabinet we had, so we needed to replace that tall cabinet. Matching existing cabinetry is difficult, and we were getting no help there. In the end, the dead appliance morphed into a complete kitchen remodel. This time, we're doing our ovens as separate units, and we're making sure that the oven stack is made with separate components, so that they could be unassembled and remade in another size. What we had before was one tall cabinet, floor to ceiling, that was impossible to alter without destroying it because of the way it was constructed.

I stayed away from the combo because if one breaks you have to replace both.

Two separate appliances, for the reason you said. Also, MWs these days are not built to last, so don’t spend a lot of money on one. Buy a countertop model for $125 or less, and put it on a shelf in your cabinetry, or on a shelf in a pantry if you have one. Just so that when it breaks, you just unplug it, and plug in a new one.