What safety precautions are needed when working on an iMac G3 with a CRT?
I can verify that the advise in that article is correct. I have discharged and serviced CRT Macs. 

I personally am not going to give you any safety advise as it is a potentially dangerous process and should not be undertaken if not confident. I would avoid servicing these machines especially if you do not have access to the official service manual.