I have a late 2008 Mac Pro Quad Core 2x2.8 Intel Xeon with Lion 10.7.5… do I need Maverick and will this hardware support the Airplay Mirroring?

It doesn't mention anything about a Mac Pro. So no.

http://support.apple.com/kb/HT5404

If your computer did support it, you would still need 10.8 or 10.9 for Airplay to work.

Welcome to the Apple community Joe.

Unfortunately, the Mac Pro doesn't support AirPlay Mirroring.

do you know of any 3rd party software that enables screen sharing for older model macbooks?

Sure.

It's out there. Do a search.

AirParrot seems to be the best of the rest from what I can gather, I haven't found any of them to be all that good.