battery cables, alternator, or PCM? i've heard all 3 could be my problem

I have a 2003 ZTS with 2.0 DOHC Zetec I-4 automatic. Just last week I had similar issues and the "!" light on the left side of the IP came on. Re-started and drove to Auto Zone to pull codes while the vehicle was running. Got 2 "B" codes for over and under voltage. There are 3 conditions that come to mind. Condition/Solution: 1) Check for loose (+) cable terminal. 2) Check for corrosion on the (+) cable terminal being sure to check on the underneath of the terminal and battery post. 3) Check your (+) battery cable for melted insulation and frayed wires where it connects to the cable terminal. If melted insulation is present, consider the replacing with Ford part no. 2M5Z-14300-BA ($92.00+ at dealer without influence) or Motorcraft #WC-95755 (eBay/Amazon $54.00+). Today, I am trying to figure out how to remove the bolts on the starter motor so I can replace the cable set. Not fun or easy DIY. Dealer price including the cable (if they can find one in a Ford warehouse) and 1.2 hours labor will be north of $230.