Will this mount straight into my existing mirror housing?

Yes — this lens mounts at factory points without drilling or modification. The housing stays on your vehicle; you're just swapping the glass.

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

You'll need to access the back of the mirror housing to release the old glass and seat the new lens. Refer to your vehicle's service manual for the exact procedure, as mirror designs vary across model years.

What if the glass doesn't seat properly after I install it?

Check that the mounting tabs align with the housing slots and that you haven't forced the lens in at an angle. If it still won't sit flush, test-fit the old glass to confirm your housing isn't bent — if the OEM glass also sits loose, your mirror body may need straightening before the new lens will seat correctly.