Different coach, but ours had an aluminum "J" angle on the wall and a corresponding "J" angle on the top of painting with velcro holding it in place at the bottom.
I would start by carefully prying at the bottom of the painting with your fingers only. You might want to check for some hidden screws, especially if there are any holes in the frame that have decorative buttons covering them.
Our new coach had what looked like some fancy new age art. When I removed it, held on as described above, it was just a poster board with some thick paint slopped on, no glass and a minimal frame. I don't think I could get a buck for it a garage sale. We replaced it with a neat 18" x 24" framed photo of Yosemite "Half Dome".