Hello & a warm welcome! 🙂
1. What video ports are on your G5, there are 3 possibilities & combinations...
ADC...
http://km.support.apple.com/library/APPLE/APPLECARE_ALLGEOS/TS2085/58846_1.gif
VGA & DVI...
http://cdn.overclock.net/2/21/215b66d1_all-DVI-types.jpeg
http://www.mytechsecrets.com/wp-content/uploads/2011/01/dual-monitor-video-card. jpg
Power Mac G5: Display Compatibility
http://support.apple.com/kb/HT2707?viewlocale=en_US
2. Does it have the same connector as the G5 has?
3. OSX Leopard/10.5.8 is the highest it can run, there are a few old PPC Linux distros that may work also.
Leopard requirements/10.5.x...
* Mac computer with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor
minimum system requirements
* 512MB of memory (I say 1.5GB for PPC at least, 2-3GB minimum for IntelMacs)
* DVD drive for installation
* 9GB of available disk space (I say 30GB at least)
Classic/OS9 Apps no longer supported.
May be available from Apple again...
https://discussions.apple.com/thread/4720126?tstart=0
Trouble is Apple no longer sells it, check eBay & such for the Retail version, not the Gray Discs...
http://www.ebay.com/sch/i.html?_nkw=mac+os+x+leopard+retail+10.5