Will this glass fit my existing mirror housing without any modification?

Yes. This lens is designed to seat into your factory mirror housing as a direct drop-in replacement. No drilling, cutting, or housing replacement needed.

Do I need to order both left and right side, or can I buy them separately?

You can buy them separately. This listing is for the left-side lens only — grab a right-side lens if you need to refresh both mirrors.

Is there any preparation or adhesive required to install this?

Installation depends on your specific mirror assembly design. Test-fit the lens first to confirm the mounting method, then use appropriate adhesive or mechanical fasteners for your setup.