Hello.I have a G5 Dual 2Ghz 150 Gb of storage and now only 12Gb left. I do a lot of video editing and need at least 500 Gb of added storage. Can I do it myself,meaning is it easy to add internal storage to the G5? The apple store guy says he would like to keep the mac for a a couple of days and that is very inconvenient for me. Thanks for any advice.