I have fulfilled all my obligations in a 1 year probation sentence in a 6 months time they said I could get early dismisal if I do soim at 6 months and was told by my probation officer all I have to do is write the letter to the judge what are the chances of him saying I can be done I just want this crap in my past and want to move on with my life

If you write a great letter and get a good judge, then yup you have a good chance; if you get a bad judge or write a poor letter then the chances are not so good.