In my rig the lens units "screw" off. Take a kitchen lid opener and push it against the outer rim. You may have to try both directions to find out which way is correct. Mine turn clockwise looking up at the lens. Only takes 10į or so to get them off.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 Jeep JKU Dragon Edition