It only took me about an hour.
I opened up my Late 2009 iMac and replaced the hard drive with a larger one. I also took out the DVD drive (which I never use and I own an external one anyway) and installed a solid state drive in its stead. I fooled around in the command line for a few minutes and created a Fusion drive from the two disks.
I used a 2006 MacBook for six years before I sold it. This iMac is 4 years old; now it has new life to serve for a few more years.
And by the way, the upgrade makes it feels fast again and like a new machine. not bad for less than $200.