The most extensive "expo" travel I have ever done was in a 2wd Ford Ranger with an Auburn LSD for traction. 2wd will get you into a lot of great places, but like Clint Eastwood said in Magnum Force "A man's got to know his limitations." As long as you know your limitations and stay within them you'll be fine. You didn't say what part of the country you lived in but I have often thought that if I didn't live in the snow belt a 2wd would be a perfect vehicle for me. There's a lot to be said for simplicity - the less there is, the less can go wrong.
A 2wd truck with a manual tranny and manual crank windows can conquer about 90% of the vehicle-capable roads and trails in the US and for the other 10%, well, if you're young and fit there's always two-
foot drive! Not only that, but a 2wd will usually get better MPG doing it (I routinely got 23-25 mpg out of my Ranger and getting it over 26 wasn't unusual. In contrast, even with a light foot my 4wd Tacoma can rarely break 22 mpg and 20-21 is a lot more common on the highway.) More MPG = more ability to travel to exotic places.
Remember that until about the mid-70's, 4wd was relatively rare, but it didn't keep people out of the back country. Heck, when I was a kid growing up in the 60's, we did a lot of our "exploration" in a 2wd station wagon! And if you go to the 3rd world, you'll find that 4wd is pretty much the exclusive province of the wealthy and international organizations - the locals generally get by with 2wd and seem to get around OK.
I'm not a tech-head so I won't comment on the simplicity/difficulty of a 4wd conversion, I'll only say that in my experience, 4wd vehicles aren't hard to find so unless you're itching for a "project" or absolutely in love with your current vehicle, you'd probably be better off just selling it and buying a 4wd if that's the way you want to go.
The most important tool for "exploring", IMO, is a map, a full tank of gas and a large supply of curiosity.
Welcome to the forums and good luck!
