Alright guys, the voltage regulator has been replaced, but it made things worse. I didn't find much at all about how to replace one, so I'll put it out there for someone else.
1.) Remove both bolts holding the alternator to the bracket, one up top and a long, backwards bolt at the bottom (head of bolt is facing the firewall)
2.) Take belt off, should be loose enough to pull it off. Mine was still kinda tough, the best way i can describe it is it's basically the same thing as taking a belt off a snowmobile
3.) Unplug wiring connectors. The connectors sit somewhat deep in the alternator, so prying the little clip things up is a little funky, but not hard when you start doing it
4.) Take alternator out
5.) Remove 6 screws on back to take off voltage regulator
6.) Install new regulator. Once installed, pull the pin out to drop the things inside down. (I forgot what they're called. Keys? Slides? They're little rectangular things with a curve at the top)
7.) Reverse steps for reassembly
Tip: The bottom bolt will only go in if the holes are lined up perfectly. I had a friend help me hold the alternator in the right spot so I could slide the bolt in. Can probably be done solo, too.
The whole process took me 45 minutes, but what followed has lasted the whole day so far.
Before I started taking things apart, my voltage was fine according to my gauge. After I put everything together again, I touched the ground cable to the negative post on the battery, and sparks shot out from behind the alternator. I waited a few seconds and tried again, this time nothing happened. I tightened it down, grabbed a fire extinguisher for peace of mind, and started the truck. It started fine, but my battery light on the dash was on. I checked my gauge, and the needle was about halfway between the middle line and the line to the left of it. I let it run for probably 2 hours, and it didn't charge at all, it actually went down a little bit. My friend and I went for a ~15 minute drive (one way), and the needle dipped down to just above the last line. I also noticed it started to hesitate a little when I first gave it gas. I took it home, and on the way, the needle went into the red/danger zone, and the turn signals started to act funny. Usually the light turns on and off right away, this time it stayed on for like a second and half, shut off, came back on again, and so on.
NOTE: I took it back to O'reilly to get the alternator tested again, and the guy said the voltage regulator was still failing. I took it to the Ford dealer down the road and told the tech guys what was happening. They said to check the PCM, the wiring behind the alternator, the alternator itself, and then take the new part back last.
NOTE #2: The last owner cut the wires to the big connector the the top of the alternator about 3 inches from the connector, and did a pretty bad job of connecting them again. The heat shrink on two of the wires wasn't shrunk all the way, showing some bare wire if you looked into it. One of the wires even had a quarter inch of exposed wire.
Thoughts, comments, ideas?