will a regular monitor (pc) work with the g4 desktops?

No problem.
The only trouble is when you want to connect the latest Apple monitors to a PC or to an old Mac, as they have the new ADC connector (adaptors exist, though)
As long as they're both reasonably new, the monitor and Mac should have no problems together, assuming you can connect it to the computer first. Watch out for ADC only video hardware on some Macs. My ViewSonic monitor works just fine, but some others might have trouble with plug 'n' play detecting resolutions. There's another thread here on this board, somewhere, that describes how to kill the plug and play crap, though.