Upgraded my eMac's hard drive today! :)
So today after using Carbon Copy Cloner to make sure everything on my internal was cloned to my external, I went a head and did the swap. Taking the eMac apart to the point where I could get to the hard drive took about 15 minutes. After that, swapping the old drive with the one in the enclosure, putting the old drive in the enclosure, and putting the eMac back together and cleaning out the inside a bit of dust and crime, took another 30 minutes or so. So about 45 minutes total.
I am happy to report that everything appears to be working ok. My old drive shows up nicely in the enclosure and the new drive (a 160GB) looks about the same as the old one did but with a lot more room free (~55.5GB free). So that will buy me some time. I could have put my 200GB one in here, but then I thought, when this drive begins to fill up, by then it might be time to upgrade to a new computer as this G4 is our most recent computer in the house, so probably should catch up a little.
A few notes for anyone wanting to do this. I didn't bother to discharge the CRT. For one thing, it is under a rubber cap anyway, but also, all the work you need to do to change the hard drive is on the opposite site of the computer, so I never came close to that part. I did have an alligator clip lead and a screwdriver that I was going to discharge it with, but skipped it. However it should be noted, as an electrical engineer, I am very comfortable working around stuff like this, so perhaps others not so familiar with high voltage and electronics might want to opt for the discharge.
Keep your screws in a row. That is, as you take off a set of screws, put them together. Next set, put to the right of those, and so on. When you go to put it back together, you can then work backwards through your line of screws.
Basically all you need is a 2.5mm allen wrench and a phillips screwdriver.
Happy upgrading!
Patrick
eMac 1.25GHz with Superdrive & 1GB RAM  250/200/160 FW Ext Drives , Mac OS X (10.3.9),  Epson 740 Printer  iLife v4 