These mirrors are large and I'm not sure what to do with them to remove them. Any advice?

How is it held on? If clips, just remove them. Wear gloves and be prepared because the glass is heavier than it looks.

If its glue or silicone then you will have difficulty. Either break glass pieces off, or cut the whole piece of drywall out. No matter what you do, you will have drywall to repair and a wall to repaint.

Try this.

Purchase a length of small multi-stranded wire cable and a 3/4' diameter dowel.
Cut a couple 3" pieces of the dowel and drill a hole thru the center. Attach the dowels to the wire cable for handles. The cable should be about 12 to 14" longer than the width of the mirror. Slip cable behind mirror and begin a sawing like action. The mirror probably has spots of adhesive attaching it to the wall. The twisted strands of the cable should "saw" the adhesive. This is probably a two person job with a third individual standing by to hold the mirror as you progress in removing the adhesive.

That's a standard way of removing windshields from a car.