Just removed mine this summer. It was siliconed-in, and was horrible to remove. One of those angle-knives should have worked, but didn't. A piano-wire cutters may have worked, but I didn't have one, nor someone to help at the time.
What did work, slowly, was to use a razor-blade paint-scrapper, from both the inside and outside, to slowly cut the glass from the silcone sealer (and what was left of the old gasket).
I picked up a six-pack of the new gasket material recently. I'd be willing to part with four rolls if anyone is interested.
