If i change my private parts from a man to a woman do i have to take any medications after if i don't want to?

No: Medications are never "required". They may be recommended, but the choice to take them is yours alone.

Some basics: If you desire a transition, physically altering your external body parts will not change what happens naturally inside your metabolism. Men create tiny amounts of estrogen, the hormone that sustains womanly features . You can remove the testis & stop testosterone, but what you describe would be a eunuch with female parts that would probably not tolerate sexual activity.