Help 2014 Silverado Transmission issues

[Soumodeler]

In a bit of a tight spot and need help. Traveling for Thanksgiving and halfway there my 2014 Silverado 5.3 with 260000 miles starting acting up. Vibrating and surging randomly, felt like it was slipping and the rpms were fluctuating oddly. It made it another 70 miles or so doing all the same things at time, but would go back to normal for a mile or so, then back to doing it.
 

I’m at my destination now and have called a couple of places I somewhat trust and have gotten totally opposite advice. One place says flush the transmission and it might help get me home on Sunday but he cant work me in due to them being closed. Other place says flushing it is the worst possible thing to do and it likely won’t work at all afterwards and he refused to do it. 
 

I did a little test driving here and I hear some whine that’s new and the transmission fluid is dark. 
 

torque converter was worked on at around 150000 miles I think. 
 

any suggestions? I mainly need it to get me 400-500 miles back home where I can have it taken to my shop I use. I know it probably needs to be completely rebuilt at this point.