If re instatement and the J W life is your aim, then sobeit. Many here would make a different decision, but your life is your own and I wish you the best in whatever you do.
In my experience, a few years ago now, the procedure went along these lines.
After attending the meetings a while the person sought a meeting with the Presiding Overseer, now called the Co ordinator, and explained the reasons and the situation. He would arrange a reinstatement committee. They meet with you and hear your case. They would liase with the Cong. that d/f'd you to get their take on it.
At the meeting they are interested in one thing only - repentance. Has the person changed their life and turned around? What steps have they taken to demonstrate this? Are they truly sorry for what they did and determined to avoid it in the future?
If they want a letter, I would keep it brief, just stating that you are now repentant and truly desire to "serve Jehovah again"
Good wishes but please read all you can on the net to confirm that you really want to rejoin that organization.