Looking for assistance we had an issue come out of no where and the recommendation is a complete replacement. Worried because we do not have any knowledge base on vehicles we do not know if what we are being told is correct! We have a Chevy Silverado 2500HD we noticed 2 days ago Truck was shifting a bit hard between 1 and 2 no big issue. On day 3 drove it about 17 miles and it parked for about 7 hours came out started fine, pulled out of parking spot and drove to corner of lot. Engine light came on and would not go into and gear easily. The engine light came on and we were able to get 1 mile down road to an auto zone and had the codes read. It’s results were P2723 and PO700. It now would not go forward or backwards. Had it towed to a repair shop and they are saying there are leaks in the lines and they tried to add transmission fluid. They are reporting a completely blown transmission. Needs to be replaced. Does that sound right that it could go from fine to dead? Please advise if this sounds correct or is there something else we need to be asking or trying. Any help, advice or assistance would be greatly appreciated we are in way over our head with truck issues vs truck knowledge.
Thank you in advance for any life-line thrown!
Kim

Chevy Silverado 2500HD
2008
We are the only owner
188,000 mileage
First approximately 100,000 seasonal towing 5th wheel
Remaining mileage to work and back mostly expressway
95,000 Powertain replaced
Exhaust Manafold replaced approximately at 140,000
We have never needed a regular mechanic the 2 major repairs were on the road when traveling

It does thank you!