I have noticed that several of my units can 'upgrade because of skill points', however how do i use them (might be a bug or something), because when i select the unit and see the 4 different upgrade areas, i can not select anything or do anything to improve their stats.

Is there a certain button, do you have to be in town... any help would be much appreciated!

Thanks in advance!

i got it... upper right side of screen :)

However - Since I'm still learning... is there a Sandbox mode in Hegemony or is that only in the Gold Version???

Glad you found it on your own. As for sandbox, I am afraid that is only in the Gold version. Its only $10 seems how you already bought the PoM.