If I were you, I'd stay away from the tristar. Parts are hard to come by.
As mentioned, parts are easy to find. The TriStar is mechanically identical to the ProStar.
You should avoid the TriStar for other reasons: it just isn't big enough for what you want to do, and it lacks storage. If you put passengers in the front you're going to take some water over the bow. I wouldn't consider the TriStar a wakeboard boat.
Having said that, I love mine!