Does my transmission needs to be replaced?

What is your question?

Okay so my dad got his first transmission fluid replaced at 150,000 miles... yes i know that was dumb but now it keeps slipping from out of overdrive into overdrive. Currently it wont shift into 3rd gear. I need to accelerate to get it going. The O/D light is flashing and thats a check transmission light, and a check engine light is on. I didn't check the code yet but I will when I can.