1996 Jeep Cherokee Damaged Tranny or not?

Back in January my transmission stopped shifting so I had it towed to a transmission shop where they told me that my transmission lines had shrunk from the cold weather and I had been leaking transmission fluid. They acted like it was a pretty bad deal and gave me a list of quotes and options from taking the transmission apart to see the real damage to buying a brand new tranny. Low on funds I decided to have the Jeep towed back home; when the tow guy arrived he jumped in my Jeep, fired it up and backed it off the ramp( not in neutral). If he could drive it off the ramp is it very badly damaged? Should I first flush and replace the fluid then see how it drives or would this cause further damage if there is any? Before my transmission quit shifting I had only noticed problems when accelerating the day before. I'm just not convinced that the transmission is completely ruined.