Trans range sensor

There was a recall on that part by Ford, I would start by having your VIN run to see if it was changed under the recall. You could get it replaced for free. The recall was #12C23. The recall was for the range sensor not shifting into reverse properly or not turning on the reverse lights when shifted into reverse. This is a link to the recall notice to dealers for the inspection process as well as how to replace the lead frame assembly which is the internal part of the transmission that causes the issue.
https://static.nhtsa.gov/odi/rcl/2012/RCRIT-12V190-9876.pdf
Now I'll guess that Ford is going to tell you no, regardless of the actual recall status. So I'll ask you what the issue you are having is, that is because there are two parts that are connected that make up the control for that transmission. One is the shift lever in the column or floor shift assembly. It has the interlock and controls the cable to the transmission. The other is the main control assembly inside the transmission that was in the recall notice above. It also has an extended coverage notice as Ford 16N02 which is viewable at this link
https://static.nhtsa.gov/odi/tsbs/2016/SB-10091155-5448.pdf
Your truck is outside the window for the repair but it might tell you if your current issue is related to the valve body as it creates several trouble codes. Now as to it being a DIY repair. Unless you have a way to access Fords programming network and have a programming tool and scan tool to allow you to program the unit once installed as the software has been updated several times and the replacement part will need the control module flashed to match the hardware parts, or it will damage them if not. it isn't really a DIY procedure.
The mechanical part of the repair isn't that bad but there are a couple tools that you will need to be able to remove the pieces that secure the valve body and harness in place.
This is a pretty good video on the process and many of the tools involved as well as which parts to watch because they can fall out while doing the job.
https://www.youtube.com/watch?v=RSPelip-gcs
Between all of the above it should cover the process.

Intermittent problems are a pain to deal with. In this case I would toss a scan tool on it and then look at what the system is doing as it fails and what changes when you turn it off. Being a Ford you might want to look at a copy of FORScan and the correct dongle. The free version will let you look at far more data than most other tools. So you could look at the shifter inputs into the control module from the shift assembly inside the transmission. Say you shift the lever into low, but the PCM sees reverse or you shift into drive and it goes into third. That might be the shifter or it's harness and not internal. However if it only does it once in a while you would need to catch it and see what it's doing.