Welcome!! If you don't mind walking a bit you can find free parking on side streets. Either along Oxford, Dublin, parallel right downtown, or across the river. There is also a parkade - it gets busy leaving so if mobility isn't a concern I'd recommend parking and walking a bit. Showing a Storm ticket also gets you free transit by bus, so that's also an option.
Concessions do take credit card. Lots of great places to eat beforehand, some may have a bit of a wait as it's Friday night so plan accordingly.
In terms of doors, I'm trying to think of how early I've been.... I am thinking an hour before game time but don't quote me.