If I am reading this right, there are two locations, the convention hall and the stadium.   Is that right?  They seem pretty far apart. How do you get from one to the other? 

They're on adjacent blocks. They're not that far apart. If you look on a map, you'll see where they are in relation to each other.

There are two ways to get from one to the other. One way is the obvious: Just exit the southeast door of the ICC and head across the street. It'll be blocked off for food trucks, so crossing is no problem.

The other is to use the underground connecting tunnel. There will be some booths there, so that route can be interesting too. 

Keep in mind that the convention also has events in the surrounding hotels. The JW Marriott, the regular Marriott, the Westin, Hyatt Regency, etc. And also in Union Station. Gen Con takes up more than just the convention center and Lucas Oil Stadium. 

2 main locations.   Events are spread out all over downtown around the convention center.
  Generally there is a ton of walking involved to get from point A to B.   During the Con I'll put in about 15-20K steps a day.   If you need (or someone in your party needs) mobility assistance one would have to account for that.   I believe the farthest point from the Northern most center of the ICC (on Maryland) to Lucas Oil is about 1/2 mile walking distance.

I'm all over the place though at the Con.   If someone really wanted to they could reduce the amount of walking they did by only selecting events in say Lucas Oil or the convention hall

Yeah the total amount of space used by the convention, we figured on the Discord, is about equivalent to the Star Wars and Harry Potter theme parks in Florida.  Much more than just the convention center and arena.