Your going to need a NP mast, NP sails need an NP mast to suit there specific bend characteristics
i think an X6 would be good, last a while and is lighter than the X3
Get a new one , you dont know what kind of life the used one has had it could break on you at anytime.
If you dont wanna spend that much get an X3.
Finally , go and see you local shop and have a chat to them.