Transmission Codes 97 Silverado

A few days ago my wife left she called back said the speedo, tach, and PRND321 indicator lights wasn't working I told her to come back and I would look at it. When she got back she said when she went to pull out that it felt like the brake was stuck. I checked some fuses, fluid, ect found nothing obvious. I started the truck and everything was working I drove it and it drove fine. She went on to visit her family with no issues. It's been 4 days and approximately 200 miles later then last night the transmission slipped a little or the RPM's went higher than they should and it wasn't a smooth transition either going into 3rd or 4th. I had it hooked up to a computer and the codes were P0740, P0753, P0758, P0785, and P01860 all transmission codes. The transmission was rebuilt about 6 months ago but of course the warrant has expired. I know multiple transmission codes can mean it's the ignition but would that also cause or allow it to slip. Any ideas of what I should try to replace first?

first, before you replace anything... check your tans fuse 20 in the dash fuse block. If the fuse is not blown and has power check the wire to make sure the power is getting to the tcc pwm solenoid connector.

I've checked the fuse I've traced the wires and found nothing

I would have the trans shop check it out for you. They should have a tool that can replace the trans computer and see if the trans will shift through all the gears. If you have battery power at the trans fuse and it sends that power to the pink wire at the trans connector then you would need to see if the solenoid pack is sending that power through to the computer. the computer grounds the solenoids to make them turn on.