For my Mac 2.8GHz Intel core 2 Duo, now 4GB 800MHz DDR2 SDRAM, 24" screen the extra 4GB of RAM kit (2GBx2) was £40.24 and as I mentioned it really was straightforward to install - there's instructions delivered with the memory kit and also on here
http://support.apple.com/kb/HT1432 Before I started I placed a towel on my desk and laid the Mac screen on top of it, removed the screws as instructed and took out the 1GBx2 of existing RAM - in quite tightly though so some force req'd. Then put in new RAM making sure I noted the way the old ones were configured but all this is explained in detail in the instructions. The static scare was taken care of by buying the optional straps from crucial and making sure I earthed myself somewhere beforehand - any pipes that are going to earth, i.e. the mains water pipe and that was that really, I checked on 'about this mac' and there it was 'Memory = 4GB' job done! The folk at crucial
http://www.crucial.com (just click on 'Download the scanner') were great so why not give it a go? It has certainly made a difference when manipulating my photographs...