'95 Riv tranny Problem

I have a '95 with 230k on it. I recently drove to Daytona for the 500 and logged almost 5000km on this trip during which the car worked flawlessly. Two days after I returned from my trip someone else was driving the car when the tranny "failed". The tranny will not move the car at all, when you shift through the gears it is as if they are all neutral. The fluid does not seem burned and I noticed no slippage prior to this even as I drove through the mountains of the Virginias to and from Florida. I took the car to my local mechanic who imediately said the tranny was done and needed replaced, his only diagnosis was pulling the selector into 1st gear and the car didn't respond, he said this was like an over ride and the car should have moved. I am sceptical of this brief analysis, any comments or suggestions would be appreciated. Thanks.