I don't think you need to add in anything because of the tren in your cycle. Some guys add in dostinex to help with sides but IMO this is not that necessary for most guys...some yes, but not most.
As for how long to run it, 8wks of tren is typically a pretty solid stint...you can run it for shorter periods, say 6wks but 8 just seems better IMO. As for max length, 12wks is a pretty long time, some can do it, other can't handle it...I would stick with 6-8wks your first go around and see how you do.