Leaf springs are pretty easy. You're going to want to jack the truck up on jack stands, pull of your wheels, and then put your jack under the side of the axle you're working on at the time to relieve the weight of the axle. Proceed with unbolting the U-bolts, then unbolting the ends of the spring. You don't have to worry about tension, because the weight will not be on the spring, and the shackles swing to where the end of the spring is. You may have a problem getting the bolts out of the old springs, but that's probably the biggest possible issue you'll run into. I had to burn bolts out before that had been on there for a long time because they rusted to the sleeve inside the spring bushing, but again, this will potentially be the part that gives you the most trouble. The rest is simple, and going back in with new bolts is very easy.
I'll add that I've actually changed springs without even taking the wheels off. Just jacked up the truck enough to relieve the spring tension and went to work. It's easier to work on the U-bolts with the wheels off, though.