Delivered fast by USPS - Done before Christmas!
My iMac was underpowered for the new OSX Mavericks and other software upgrades. This was slowing it down since it began using virtual memory as a substitute for RAM.
Piece of cake! It took only a few minutes. Fortunately the iFixit Guide clearly stated to make sure I heard and felt a click on proper insertion of the chips. Otherwise, I might have been disappointed.
Get some good advice from Apple and iFixit and whenever possible, fix it yourself. ALSO...this was the first time I flipped my iMac over this way and I found the vent holes were becoming clogged, so I vacuumed them for better ventilation.