In our RV, the rear bottom of the microwave hooks onto a frame screwed to the wall behind it, and three bolts hold it up from above. Those bolds are hidden under the floor of the cabinet above, so I have to remove the cabinet floor to access those bolts.
By the way, I'm older than you and have removed and replaced the microwave three times. The first time, I had it repaired, but the repair only lasted one year. So when the second one failed I replaced it, and when that one failed I replaced it with a more expensive Microwave Convection Oven. That one has lasted for years, and DW likes it better.
BTW, since in our setup, the microwave swings down from the back lip when the bolts are removed, you might want to block it up before you remove the bolts then work it down. I used a stack of books to do this.
YMMV