three hours before the game 'touchdown city' is open at the wamu theater which is basically on the southwest side of the stadium. my advice is to head down the alley there.
Here's my 'game day' suggestion as long as you don't mind a walk:
Starting off at the stadium, occidental will be a flood of people and vendors and team shops. This is a good place to grab some grub from the street vendors (most of them are pretty good) or check out the pro shop, or other apparel stores.
three hours prior to the game you can also go into the WAMu theater there and there will be various events happening. You can check out the game broadcasters who are doing the radio pre-game show. they usually have bands or something going on.
If you follow the green path I laid out down to utah street that is a nice little area full of tailgaters, although I have no idea what it will look like for a thursday night game. but in general I find that's a nice route to pass through if you just want to mingle with other fans
I recommend getting into the stadium no later than 90 minutes prior to kick off. If this is your one shot in the known future to see a game it'll pay off to find your seat, get your bearings, scope out what's near your seats and otherwise just check out the stadium. If you've never been to an NFL game before you'll want to be seated an hour before kick off to watch the teams come out and warm up. That hour will fly and it'll also get that atmosphere seeping in so by kickoff you'll be chomping at the bit. Note that there are elevators, along with a large cargo elevator located in the NW area of the stadium - so if you have seats in the upper level jump on that to save you some walkin.
I know a lot of people say that the NFL experience is better at home these days with HD TV's and such.
But for my money there's nothing like game day and being there. And these past couple years of seahawks football have been electric, to the point where you can literally feel it in the air.
Bring to the game:
-if you need a bag make sure you have one of the NFL approved clear bags
-try to smuggle in a plastic pop cap from a bottle of coke if you plan on buying one at the stadium. They take the caps away when they serve them to you so people don't throw them or slip on them.
-if it's raining bring a small towel or paper towels to dry off your seat; ponchos are available at the team store or kiosks
-tea with lemon a few times the 24 hours prior to the game will help those vocal chords =)
-have fun, be loud.