Oddly enough, I've actually been to Baltimore--a couple times. I've actually gone to a game there, too. Titans vs. Ravens. The week after the Titans beat us.
Anyways, it's been a few years, but Baltimore is decent. I actually really enjoyed it. It has the usual city stuff: food, shopping, exploring! The main attraction is the Inner Harbor (pretty darn cool). There is also the National Aquarium, paddle boating (probably too cold for all that, it's in Dec. right?), and a great dive bar called Pickles near the stadium that has crab topped burgers.
I remembered some of this, but also texted my friend about it to help you out.
Her number one response as far as advice: "Try not to get shot!" LOL. She's crazy, but I'm sure you'll have a blast! Don't let those fans scare ya! You're a Viking!