Will this fit my existing mirror housing?

Yes. This is a direct replacement lens designed to mount into factory tow mirror brackets without modification. Your current mirror housing stays in place.

Does the glass come adhesive-applied or do I need to secure it?

Mounting method not specified—test-fit first to confirm how your factory housing accepts the lens before committing to your fastening approach.

Can I use this if my mirror arm is damaged?

This product is the lens only. If your mirror arm, bracket, or housing is bent or cracked, you'll need to address that separately for a proper install.