Will this fit if my mirror housing is still good?

Yes. This lens drops into your existing housing. As long as the backing and frame aren't damaged, you're good to go — no new housing needed.

How do I remove the old glass without breaking it further?

Most mirror lenses are either glued or held by a small retainer clip. Gentle heat from a heat gun softens adhesive; a plastic pry tool works to separate it. If your mirror has a clip, check your vehicle manual for the exact release point — it varies by model year.

Do I need to prime or paint this before installing?

This is glass — no paint or prep needed. Just clean the backing of your housing before seating the new lens to ensure a clean bond.