I can't second guess your doctor because not sure about the rationale...it is a safe change, and wellbutrin is a great medication for a lot of people, and if you agree with the change you could consider it to be an experiment, and change back if necessary.
I'm not sure about the medication but that is something your doctor may be able to help you with. I'm not sure what is behind your T's rationale for medication change but you may like to take your concerns to them as well.
If you have been in therapy you not require as high a dose at the moment.
This is something that needs to be discussed with your treatment team.
The doctor here will be better able to advise you about the medication, etc.
Sorry I couldn't be more helpful.
Take care.