Though not trivial, it is something you can (normally) do at home...

1. Remove starter. Disconnect the battery cables (all of them is my recommendation) first. I often pry off the RTV on the battery starter main cable and remove the cable there rather than pull the cable. I used to always pull the cable but I've gotten lazy, and RTV is cheaper than spending a lot of time on the cable.

2. With starter out:
   1. Remove big cap plug (looks like a nut or bolt) on the nose end of the starter in line with the solenoid.
   2. Remove the battery strap (only from the solenoid, bend it to get it out of the way)
   3. Remove the starter strap (from both solenoid and starter, it is too short to take off otherwise)
   4. Remove the four nuts on the end where the terminals are. Discard the O-rings.
   5. Pull out slightly the end cap and remove the screw holding the wire to the terminal on the inside of the cap piece. Do NOT stress these wires!
   6. Complete removal of the end cap. If it doesn't come off, check why don't just yank harder.
   7. Carefully burnish the two main terminals on the end cap, to shiny copper. Clean and degrease. Any oil or grease will contaminate the contacts and lead to premature failure.
   8. There is a small metal disk inside the solenoid housing. This must also be either cleaned or turned over to the other (fresh) side...
   9. Stick an allen wrench into the shaft of the solenoid where that big nut was. There is a nut inside this end, do *NOT* remove or loosen or tighten this nut! If it is moved, it is necessary to readjust the solenoid, a proceedure that is a PITA!
   10. While holding the allen wrench, at teh other end lossen and remove the nut holding the round disk to the shaft.
   11. The nut will come off, along with a washer, the disk, a spring, and another washer.
   12. If the reverse side of the disk is 'new' or unused, turn the disk over and reassemble. If this process was done once before then both sides may be equally 'bad'.
   13. If you wish instead of turning over teh disk, you can clean it up carefully. The original disk is plated, however I have not noticed any issues with damage to that plating. I clean with a small (wire) brush in my Dremel tool.
   14. Reassemble the disk/shaft assembly. If the locknut doesn't go on tightly (don't tighten it down too much, but is must have some drag to keep it on) replace the lock nut. This locknut is not a nylock nut, and should be replaced with the same type. A nylock nut (the locknuts with the small nylon bushing) will fail due to heat, don't use them here! Order of assembly: inner washer, spring, disk, outer washer, nut.
   15. Remove the allen wrench used to hold the shaft in the previous steps. Replace the cap plug removed eariler. There is a sealing (fiber) washer on the plug which should be in good shape, if not replace it.
   16. The end plate gasket should be in good condition. If not replace it.
   17. Partially assemble the end plate to the solenoid, and re-attach the wire to the terminal inside. If you forget this step your solenoid will fail within a few starts, so it is vital that you reconnect it! (it will seem to work, but the windings will burn up due to excessive current)
   18. Press the end plate fully on the solenoid.
   19. With new o-rings install the four nuts.

3. Replace the starter in the truck. This step is very important, if you forget it, it will be hard to start the engine. Trust me.

4. Test. If it works, have a beer (or Coke, or Pepsi, or whatever...) If it doesn't work, figure out why!

Peter H.