Not sure about GQ's but with Navara's and Pathy's (and most other electric mirrors) you can replace just the mirror, so I'd say most likely you can replace just the mirror. You can get mirrors from Nissan dealers... or off feebay perhaps.
last week I replaced the glass in my l/h elec mirror. Cost $25 from the local glass shop to cut a piece, I just gave them the smashed one and the glass carrier to match up. Also fixed up the loose motor mounts at the same time.