My early 2009 iMac was really lagging. I hated the ideas of buying a new one when most of the hardware was still in great shape. Therefore I decided to upgrade the hard drive to a solid state.
Great! The performance has been fantastic and it really has given my computer and new life. Working slowly it took me about an hour and a half to replace the drive. The iFixit guide was very helpful.
Make sure you have compressed air. When the LCD screen is removed it is a great opportunity to clean out some dust!
Phillips #1 Screwdriver
Heavy-Duty Suction Cups (Pair)
TR8 Torx Security Screwdriver
TR6 Torx Security Screwdriver