how do you figure out your gear ratio? Open up the cover and look at the gears(teeth?). Is there any visual way to tell?

You can jack up the rear and spin both tires one revolution and count the driveshaft revolutions. Slighly more than three turns of the driveshaft would be 3.08, three and a half is 3.55 etc.

Or if you do have the rear cover off anyway, count teeth; ring gear teeth divided by pinion gear teeth = ratio.