Its not hard at all. I had the 60gb and went to a 160gb when it just started to die. I needed some info from the old drive and didn't have an enclosure at the time. I bet ive replaced it 3 times. Just open the cover, take out the screws holding the base in, and remove it from the drive bay. It has a rubber cover on it, im not sure if its for heat or shock or something, I couldnt get it to fit on the 160gb so I left it off. On the thermal paste, i didn't need to add any. I tell you what, its easier then the new imacs. For me it was not that hard. Took maybe 20min. Hope that helps