Ok, if a 13 year old can understand this(which I'm only 13) you can. The "middle thing that spins" is the rotor. The thing that "bounces inside the distributor" I'm guessing from your description is the points. If those are sparking then you know that the points and the condenser(little can on the other side of the distributor) are good. So, if all of that is good, inspect your sparkplug wires and make sure that the order of them connecting to the cap is right. Also inspect your distributor cap for burns or having oil on the contacts. If the order of the sparkplug wires, the distributor cap, and the sparkplug wires themselves check out ok then get a new coil.
***** Before getting a new coil you can do a test to see if it is good, providing that the coil wire is good. Disconnect the coil wire(wire coming from the coil going to the middle of the distributor cap) from the distributor cap and, holding the metal end(with the dust boot pulled back) CLOSE(not ON!) metal, as long as it is clean, doesn't really matter if it has paint on it if it is clean, have someone crank the engine over. If it sparks than your coil is good and you have other problems, probably fuel.
Also, what year is your truck? Model? Engine year?(if you know it has been replaced)
Sorry if that is not clear but I did my best. Someone else will chime in.
P.S. I was a lot worse off than you. My engine was stuck, condenser was good but points were bad, coil was new(due to previous owner), but sparkplug wires were completely horribly bad. You're going to learn a lot and hopefully get it started
