Replacement heated wing mirror glass

[Ga33a]

My heated wing mirrors don’t work. There’s power to the doors so I’m assuming that the heating element has burnt out. I’d like to get them working ready for the winter so can anyone advise:
1. Where’s the best place to get replacements (I just need the glass not the whole mirror).
2. How do you get the old glass out? In the past, on other cars, I’ve simply pulled and the glass and it’s backing plate have popped out. Is this how it works on a Caddy? Just want to be sure before I end up doing additional damage.
thanks in advance for any help.

[NZDubNurd]

Is the adjuster switch set to the heat position?

Unusual for them both to be burnt out

[Ga33a]

Hi, yes definitely in the heating position but they're both stone cold. I know they don't operate until the temperature is below a certain figure but when I tried them (to clear the condensation on the glass) the multifunction display was showing 6 degrees.
I would have gone looking for a fuse but according to other posts on here the mirrors are on the same fuse as the windows and they work OK.