It probably won't be easy, due to age and heat, but , The glass lens can be removed by turning it counterclockwise, like the top of a jar.

Chances are, the lens has seized to the casing and won't unscrew, like it should.
At that point, most techs would break the lens, clean up the glass and replace the bulb and lens.
The alternative turn power off the the range, slightly pull out and twist the assembly, until the spring loaded clips align with the "cut outs" in the oven wall, press down on the clips with a flatblade screwdriver, or simillar tool and tug on the assembly.
Remember to use a little vegetable oil on the threads of the lens, and don't overtighten it when you install the new comonents.

Good Luck,
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