If you've got an alternator and a charging problem you can drive your truck to Autozone or many other national chain FLAPS and they'll test your charging system for free. I think you'll probably have an alternator. It may turn out that your alternator and battery are fine, but your problem is a short you've got somewhere.
There are several discussions here on alternators and regulators which seem to answer your questions, but they aren't all consolidated. If you find some time, I'm sure everyone would appreciate it if you could read them all, do some research and then write a consolidated tech tip for the next guy that comes down the line with the questions you have.
For now, if you have an alternator you probably don't need to change anything in they way your system is wired.
If you have a generator and want to upgrade to an alternator, you would be best off with a three terminal rather than a one terminal.
A single terminal alternator is easy to wire and easy to replace the generator with. You bolt it in and run the one wire to the battery or starter post. If you have an ampmeter, you hook the one wire to the ampmeter first and then to the battery or starter, that way you can measure the flow of amps to or from the battery. (charge or discharge)
A three terminal is a bit trickier, but not much. You hook it up the same way the single wire except you have to deal with the two other terminals. One terminal hooks up to the 'first'terminal on the alternator (the one that goes to the battery/ampmeter), which is easy. The other of the two extra terminals hooks up to the 'on' side of the ignition switch, or the voltmeter/idiot light and ignition switch. It is important to have a diode in this wire. The diode's job is like a plumbing check valve, it allows flow of electricity betwen the switch and alterntor in one direction but not the other. If you want to get fancy you could connect the 'first' extra terminal to an terminal block that all the accessories are hooked up to. Doing it that way would take advantage of the external sensing capabilitys of the alternator which make the charge it puts out vary depending on how much the accessories are drawing. Alan Horvath's website has a good diagram of how to hook the 3-wire up either way.
I don't think anyone here has posted anything on externally regulated alternators and I've never seen one.
Externally regulated GENERATORs are what pre 1963 vehicles came with. There are lots of posts on those 'cause they were stock on most of the bolts. The trick with them, as I understand it, is polarizing it when you replace it, and adjusting the external voltage regulator if necessary.
