Hey - 64k miles is low for an 11 year old car! Sounds like a good find.
You can set the
ScanGauge to update quicker than its default rate, but it doesn't "remember" the setting, and you have to do it each time. I think it's under: MORE > MORE > RATE (? ... check your manual if that's not right).
As for what to expect from the car, it depends on what kind of driving you're doing. This should give you an idea what to expect from highway speeds in decent weather (warm temps).
From:
Speed kills: testing MPH vs. MPG in top gear - MetroMPG.com
That graph is with the stock transmission, and a couple of aero mods (partial grille block, rear wheel skirts).
Welcome to the site!