Will this work with my car's existing mirror controls and heating switch?

Yes. This lens connects to your OEM mirror heating circuit — flip your existing defrost switch and you're good to go. No new wiring or module needed.

Do I need to remove the entire mirror assembly to install this?

No. This is a lens-only replacement. You pop out the old glass, set in the new one, and secure it. The mirror housing and motor stay in place.

Can I order just the right lens, or do I have to buy both sides?

Just the right. If you need the left side later, order it separately — they're sold individually so you only replace what's damaged or needed.