1999 Monte Carlo Stuck Torque Converter

1999 Chevy Monty Carlo, 95k miles, automatic transmission, 2 wheel drive, no strange sounds or fluid leaks. I have a check engine light on and the code was a stuck torque converter I believe.

The only problem I've really seen with performance is when I just start my car. If I try to go into drive or reverse, the engine revs a lot and the car moves very slow. It only does it when I first start my car and I think its better if I let it warm up. The only other performance problem is that it's shifting a little bit harder than it was a few months ago.

Only relevant service issue I can think of is that I went to Valvoleen and had my transmission fluid changed, and the fluid was thick and black after only 3 months, I'm not sure if my transmission did that or if they put old fluid in my car. They redid the service for free and the fluid looks good after a month now.

Thanks for you help!