"Do I need a special RV microwave?"
There is no such animal.. Though if you want one a Panasonic Inverter model might have some advantages. (Panasonic makes a line of microwaves that have a very advanced power system, they convert the incoming 120vac to DC, then invert it back to AC and in so doing control the power of the microwave as well as clean up MSW power if you have a MSW inverter).
NOTE: these are "Home" type microwaves.. I have only seen one of them, in a park I frequent in the family center.
In my motor home I have a "Dometic" but if you open the door you find it is a common, off the shelf, LG microwave  (Lousy Goods, don't work right less you modify it, which I have the skills and tools to do and did) (Note Dometic sells many different Microwaves, far as I know only this model is an LG).
They modified it for RV use as follows.
They attacked some sheet metal so the exhaust fan blows through the front grillwork/mounting plate they attached.
I can replace it with any microwve of the same size,  I may need to bend up a bit of sheet metal is all,, or even a different size if I make adjustments to the grill/mount.
Nothing at all special about an RV microwave.