Answer:
The fact that you even ask the question shows me that you do not have the knowledge, training, or skill to rebuild a transmission. It takes training and skill to accomplish this difficult repair. Leave this repair to a professional.
Answer Two:
Even if you have other mechanical experience, I would still agree with the above answer. They are extremely complex machines and to rebuild them, at the minimum (in my opinion) it requires an understanding of how they work. Also required are special tools for removing various parts.
Click on the related link below to see how complex these things actually are. This complexity is the reason a professional (with all the necessary tools, understanding and skills) will still charge thousands of dollars.