If you find a shop who will charge you $100 for replacing a switch on older transmission with 3 owners and will guarantee it will work fine, I want the phone number for them.
When I had slight glitch on my 6-sp Ford manual, that most likely would require replacing a spring on gear holder, no shop would quote me for anything less than total transmission rebuild.
We are only humans.
Now Vinsil has a point that those trucks usually are chipped out of their brains. I read it all the time on Ford Forum that new owner after trying figure out strange acting finds a hidden chip under dashboard.