Hehe, yah... the Tank! I love that thing.
Anywho, I can't speak for THIS upcoming event.
But I was on the zombie team at the LAST Left 4 Dead (Oct. 30th, 2010).
In THAT game, the tank was slow. Any human player will easily be able to outrun it. Just don't run your way into a room with no backdoor.
As for taking it out, there is no way to "kill" the Tank. But it can be stun with grenades.
Either a nerf rocket (make sure it's SOFT!) inside of an M203, launched by a gas grenade shell (with NO BBs inside of it). That stuns it for 30 seconds.
Or roll (not throw... roll) a grenade near the Tank's feet, wait three seconds, and call out "Bang!" While your team's moving, count out 1-mississipi, 2-mississipi... you have10-mississipi's to get away.
Also, there are some doors the Tank can't get through. The bugger's too tall, and he can't duck low enough to clear the top of the door, hehe.
Just my own experiences, hehe.