It is an easy mod. I suggest before buying a new conv/micro that you remove the old one before measuring. In the Forest River Class Cs we found that the face frame around the cabinet housing the microwave could be trimmed about 1/2 to 3/4 inch on both sides and the top thereby substantially increasing the number of new model selections (based on size) that would work for the conversion.
Also, by removing the old one before purchasing the new, you can decide if you would like to vent the new to the outside. Thor should be able to provide you with the sidewall diagrams so you can determine what is in the wall behind the micro.
US Army (Ret)
2020 Entegra Accolade 37TS
2019 Jeep Grand Cherokee Trailhawk (Toad)
FMCA - F432054