Hi. You don't need to take the fixture out but now that you have it's probably easier. The lens is just pressure fitted onto the housing. Took me a while to figure it out. Tried twisting the lens to release it. Our Jayco was like that. A fingernail or maybe something thin that will not chip or crack the lens gently prayed between the lens and the housing will work. When the fixture is still in the ceiling you can pull it down enough to do it too. The lens just pushes back in.
FYI. The G4 20w bulbs in Home Depot are almost $6 each. I got pack of 10 on Amazon for under $6
Also. The recessed light lens in the cabinet above the TV, if you have it, is a twist type. Bulb is same as ceiling? Learned that after I broke one of the clips trying to get it off. I had 3 ceiling bulbs and that one go in one weekend. While on the subject I had a hard time finding the 1076 bulbs for the hanging fixture over the dinette. No auto part store had them. Also bought on amazon. KOA store did have though.
Hope this helps.