Someone has just smashed the side mirror off your perfect Nissan Altima that you parked on that busy road you know you shouldn't have parked on anyway, so now it's up to you to repair it— unless you want to pay an overpriced mechanic, who will charge you for parts, labor, and whatever else he thinks he deserves. If you're up for repairing your side view mirror by your lonesome, for cheap, then this video by Richpin will show you the exact steps required to fix your Nissan Altima's side mirror. Make sure you buy the right replacement mirror for your make and model. Be careful not to damage the electrical connection when installing.
Specifically, this is for a 2002 Nissan Altima, but could be applied to most Altima vehicles. And he shows you the passenger side mirror (the driver's side mirror is exactly the same)