You're right about the first four digits.
The last digits (suffix) are the revision level of the PCM. It rolls with hardware changes as well as calibration changes. The dealer can indeed help with getting the correct PCM.
I would strongly discourage you from doing the PCM swap yourself unless you have the NGS (or whatever diagnostic/programming tool Ford is using now). The VID block needs to be populated with tire size, axle ratio, driveline, trans type and engine (to name just a few items). The PATS programming may give you trouble...depending if you have two PATS keys.
This is something that if not done right will cause you to pull your hair out. The physical swap is easy...it is all the programming that needs to be done that will cause you difficulty if you don't have the tool.
2008 F-150 XLT, 5.4L 3-valve Triton, 4x4, SCREW, 3.55 axle.
Edge CTS - Level 2
for my gallery