Can settings for my VGA port be changed?

I have an iBook G4 with a broken screen and have been mirroring to an external monitor thru the VGA port. It works great, but I seem forced to use 800X600 resolution. Is there a way to change this, or is it the hardware itself?

That depends on your monitor and if it is being recognized correctly.

Open up System Preferences - Displays

The maximum resolution supported by the video card is 1024x768.

The settings are set for 1024x768 in the preferences (not that it matters - no screen) and there's an overlay window that lets you choose settings for the external mon, but nothing higher than the 800x600. This monitor definitely goes higher than that and i've tried others, and they are all recognized the same. So I wondered if there were simply limitations to mirroring on this computer, and if there was a firmware upgrade that could circumnavigate the issue.

It was shipped from the factory able to provide 1024x768 to an external monitor and it only allowed for mirroring. It had no extended desktop mode.

Possibly it's not recognizing your externals properly. You could try a different cable.