I just bought a 99k in a cabinet on Craigslist...only $20! Cabinet needs refinishing tho..... Anyway, it had been years since I changed a light bulb in that type of light. But, I didn't have any problem removing the lens.
I removed the light from the bracket so I wouldn't be putting a lot of pressure on the bracket...& so I could see what I was doing a little better. Pushed in on the lens...hard. Turned & it came out! A good tip is to wear rubber gloves...it gives you a little traction so you can turn it easier.