If Apple was willing to sell replacement parts to the public I would feel better about these types of upgrades. I don't mind doing the work but it's always stressful knowing you don't really have a Plan B if something goes wrong. I tend to only do these upgrades near the end of the machine's life cycle so if I totally bork it up I won't feel too bad about it. If you're lucky you might be able to find the parts on eBay. I've been casually studying the economics behind this. My theory is it's entirely possible to buy a brand new iMac, take it apart, and sell all the individual components on eBay for a pretty decent profit.