For an inexpensive backcountry aircraft, don't buy a plane because it's for sale cheap. There's a reason it'll be cheap and you will get frustrated pouring money into a plane, especially when it is grounded for maintenance half of the time. Don't discount experimental aircraft, just be very cautious. Pre-purchase inspection!
Learning to fly the backcountry? Get instruction and go about it slowly and deliberately. Learn slow flight, stalls, spot landing, and how to read the weather. Just remember, the skills are important but experience and judgment will keep you alive when a beautiful flying day goes to hell.
Hey Raven! Good to see another Mainer around. We have several on this board. Do a search for "Maine" and they'll pop up. Have you checked out the guys at CCAS
http://www.flyccas.com/ for instruction. They are up in Millinocket and I think Old Town.
Maine is easier than the West because we don't have huge mountain ranges to contend with, but still fun. Last winter I was following one of our local pilots in his Champ. He showed me how to land on the frozen Kennebeck River and on the Pleasant Pond snowmobile trails. My first off-runway excursions in a small plane and I loved it.
I'll be back from Afghanistan next August so then maybe we'll run into each other at Twitchell's. I normally fly out of Merrymeeting, 08B.