Ford - Taurus :: 2004 - Torque Converter Not Working Properly

My wife's 2004 Ford Taurus has been acting up. It shudders sometimes at stoplights and also while driving sometimes. The auto parts store plugged in the computer and said it was the torque converter not working properly. We took it to "The Answer" in Evansville, Indiana for their advertised free diagnosis. They checked it out and told us basically the same thing. The torque converter was acting up. (Slipping? Catching? I don't remember the exact details...)

They said the remedy would be a big expensive job (install rebuilt transmission? Replace torque converter?). Is there anything we can do to prolong the inevitable such as fluid, filter change...flush...additive? We are resigned to the fact that we will need to buy another vehicle but wonder if we should buy one now since the Taurus may only last another few weeks or can we put off buying another car because the Taurus may last another six to twelve or more months.