Should be easy,the Imac G3 is known for Flyback transformer failures, once this done the Imac is more or less useless.
I have been given two units with that problem,kept the logic board, drives and casing (still have those...but no inner bezel
)By the way,sorry but apparently the right side panel seems to be broken too. :'(
Working with CRT is no problem, if you discharge the unit properly.
Changing the HD is a piece of cake, once the bottom casing has been removed.