I'm still using a 2010, and while I did upgrade to an SSD and added some RAM, it's still going strong. The only thing making me consider upgrading is that OS X upgrades stopped supporting it.
On the 2010 models upgrading the RAM or hard drive just involved a specific screwdriver to take the back off. It took approximately 5 minutes to do at home.
Pretty sure its impossible to upgrade the Air unfortunately.
