It just pulls off. You may want to wedge a strong flat plastic object into one side of the cover and GENTLY pry the piece loose. I was able to use my fingers, but it wasn't easy.
The covers on mine are frosted glass with a lip around the edge held in by spring clips, but the glass is pretty thick, so I would imagine hard to break. I've had them off several times, and never broken one.
While you're up there, I would consider replacing the halogens with LED; MUCH cooler running temp.
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!