Standard range/cook top area is 30" and so over the top M/W's are 30" wide, putting one in place of a range hood is typically not a good idea as it hangs WAY to low, needs be 17" min off the range surface.....
any Certified Kitchen Designer/CKD that puts a 27" cabinet width above a cook surface is in fact against national fire code, which is somewhat of a comic in that the adjacent cabinets can catch on fire just as easy.....
We have an island range with large range hood up high, Linda can watch TV and share in family life while cooking dinner....large open space concept....no dining room eat in kitchen flows into main living room,
M/W's these daze are cheep, even the wall hung variety....I built a deep open shelf and fancy cabinet design to hold our M/W nice and up about 15" off the counter top on the end run....so we have a counter top model....150 bux 1200 watt unit....
I remember the old LITTON INDUSTRIES unit we bought back in the early 80's paid like 800 bux for the thing, I had to put a control panel in it, and a Magnatron tube.....it quit heating up fast and so lost power....no more 20 second coffee....
OH< one more thing, do NOT attempt to fix/replace your doors....
they are a radiation shield and as such if messed up, you can get yourself spread with M. Waves and do yourself mucho bad harm.....
back decades ago a buddy from the Navy told of some ET chief and a Cook getting into it over something, the ET guy was working on the ship's radar, the cook over rode the safety, and turned on the radar, and killed the guy....dead before he hit the deck......