Time to go, microwave of mine

My microwave was whatever was going at costco at the time, back in the late nineties. It had some burps after a while, as it had gotten into knocking, and when it did, I looked online and the answer was to change the power level. I'll guess 2007.

That worked. And recently it's been knocking again and I see online nothing about power levels, but all about death of the appliance.

I looked around online, thinking it's time now or soon, and bought a new one for about half of what I paid for the first one.

I have two questions -

a) was my last one really cooked out?

b) how to I trash it responsibly?