I've always had a soft spot for the Tristar. I just about bought one instead of the PS205. I'm glad to see you're giving her a second life.
I can't help you with the skins. I did the upholstery from scratch in my last boat and it wasn't bad (took a class and learned to use a sewing machine) but I think the Tristar would be pretty complicated.
Some mornings it just doesn't seem worth it to gnaw through the leather straps. -Emo Phillips