Okay, gonna show my ignorance here. Personal trainer? How do I access that? This is something different than an iinstructor for the obstacle course or punching bag, right? And what does personality have to do with it?
And what is this Yummy for learning cooking? Only place I have seen that is when sims smell food and say it smells yummy. Surely they are not learning to cook simply by smelling.
Okay, you can only get a personal trainer if you have the University EP. Then take your student to the gym. If you have no body skill points it shouldn't take long before you get a coach to help your Sim, or rather.. a personal trainer.
Now, The Yummy Channel will teach your Sims to cook and all they have to do is watch that channel on television. So if you have a couch potato you'll learn really fast. Expect some early cooking failure, like burning an omlete the first time they cook one. Just cancel the serve and make them throw it away and have them make another omlete. It will be a good and bad memory for your Sim.
Hope I helped.
SimMoon