I see two problems. The first is that the game doesn't keep track of all the data you'd need. I assume you mean total ore harvested as opposed to how much they have on hand when it's over? And if you want to display a graph, don't most game graphs require some sort of history to those values? In which case you'd have to set aside memory to hold these values, hook at least one, and possibly a few code locations to get the history/running total to update correctly. Not completely unreasonable, but not exactly trivial either. It certainly begs the question as to whether it's worth it or not.
The next issue is then to actually display the data. That also strikes me as a somewhat nontrivial task. Maybe the code was written flexibly enough that it shouldn't require too much patching, but then you'd still have to figure the code out before you'd even know. Hacker might already know how to do this, but I sort of doubt he'd have really bothered to spend much time looking into the details of post game stat display without a good reason. So yeah, this second part is also probably a substantial time investment.
My advice for when simple nice changes like this require so much patching, and the source code is not available, is to start considering rewriting the whole game. Well, not for this patch alone, but for this and the many other patches for fairly simple things like this that actually require substantial effort to change.
