Of course, the best way to learn is get out there. :)
Many local colleges, outdoor groups, outdoor stores, etc. offer basic classes for free to little cost (enough to cover the materials).
I took a map and compass class through the RI chapter of the Appalachian Mtn Club back in 1997. I learned off a topo with 10' contours!!!! :D
But, the basics stuck with me and those original lessons apply whether on the Continental Divide, the Utah dessert or in the gently rolling terrain and woods of my native RI.
We did one class day and one field day. The field helped A LOT.
Oh yes..realized you asked about GPS, too
If you can count to 10, you can use a GPS (UTM coords!)
This site works well:
A GPS is basically for UTM coordinates.
You can learn more of an overviews of the bells and whistles at a class typically offered at REI, but it is all about base 10. :)