after replacing the transmission shift cable and PCV valve the overdrive light is off, and blinking?

Off or blinking? If the shift cable wasn’t adjusted correctly after replacement, the PCM may be seeing that the gear lever doesn’t match the actual transmission range. It takes a special tool to do the job correctly. Check out the images (below). Let us know how it goes

I'll let my personal mechanic know and we'll definitely get back to you! Thank you so much.

You are welcome, please let me know what happens

I will. He's coming over today

Thank you :)

Well, my guy came, checked everything, tightened a couple loose screws, and stared it up. Overdrive light is still blinking.
Could it be a safety light telling you that something could be wrong with things for the transmission so you don't do severe damage to it?

Gears are shifting like they should be. It's about a quart low in fluid. Could that be the issue also? It's not dirty.

Since the overdrive light is blinking lets run the codes to see what we are dealing with. This guide can help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please go over this guide and get back to us.

After installing the transmission gear shift cable and checked several times the truck will not go forward when I put it in drive.

Did the transmission work before the repair? If so the cable can be not adjusted correctly. On level ground with the parking brake on, I would remove the cable from the shift arm of the transmission, and put the shifter in neutral, then put the transmission in neutral and see if the cable lines up perfectly with the shift level of the transmission.