Dirver side mirror broke today

May have to pull inside door panel to do it. Check with hyundai

Maybe this can help you with your mirror. https://www.youtube.com/results?search_query=2012+kia+optima+side+mirror+replacement

If the mirror housing is in place, Have one cut to fit. Glue it in. If the housing is broken, replace all of it. You can't fix a broken side mirror. Tried to many times.

You don't say if it's just the glass mirror that's broke or is the housing cracked as well.
If it's just the glass mirror, it's held in place by double-faced adhesive tape. You can buy a replacement from a dealer or on-line. To get the old one lose, heat the glass with a hair dryer while pulling on the glass with a hooked tool.

pop off the inner plastic panel on the inside of the mirror mount area and you will see 3 bolts/nuts the remove the mirror.

The part can be bought on ebay or even craigs list, Many junkyards have them too a good price is $20 but their just under $100 new

Most auto parts store have replacements with self adhesive tape on the back. Peal and stick, just remember to clean the surface good. Also, they may need to measure the passenger mirror to give you the correct size.

That dependso on if the housing itself is broken then yes. If the face plate that is attached to the mirror itself is flapping around then maybe. If it is just the mirror, just go to your neighborhood auto glass shop and but a "Ready-Cut" mirror for a small amount of money. they come already cut to fit perfectly. As for removing the old glass, take a very small flat screw driver and pry the glass away from the face plate. Once completely cleaned out use the adhesive from the ready cut and place them on the face plate. Next press the new mirror onto the flace pate, being careful not to press to hard or it will snap it in half.

For paint, take your paint code off the inside lip of your dirver side door. Take the number to your local autoparts store, and get the matching paints (unless you need a custom job as in metallic flake). You'll need a clear coat as well as your base.

If the metal pivot arm is not broken you can just replace the glass and plastic housing. To remove the glass you tilt the glass down towards the floor and use a wide plastic or wood bladed object to prise from behind, the glass should pop off from its clips. Remember to catch it if its not damaged. To remove the housing once the glass is out you need to look underneath the mirror unit, there you will find a small plastic bung, gently prise it out and then use a long small flat bladed screwdriver straight up inside the hole and lever towards the front of the car whilst lifting straight up on the plastic housing, this should then lift off. To replace just slot the new housing on and click into place then fit the glass back, remember to connect the wires first if it is a heated glass.
If the metal pivot arm is broken then you will find the remaining screws behind the plastic trim inside the vehicle.