You should do a timing belt change at 1k hrs, it's well documented how to do it here on the site, there are several posts by guys with a lot of first hand experience with automotive versions of this engine. It's not that big a deal for an experienced Toyota mechanic. I would not be scared of the boat because it got a timing belt, there's still a good 2k of engine hours if they changed the oil once in a while. Drive the boat, if it runs smoothly it's probably fine. If not, change the plugs even with cheap ones and drive it again, it'll probably be fine. If the gauges including the oil pressure gauge are flakey, it's a common problem with many boat manufacturers of that era.
The parts will be available until the end of this year through this website, after that, who knows? Capt Rick, what's the state of the union on parts availability? Could TMS interest Skidim or someone with purchasing all or some of the inventory? Maybe not everything but if fuel pumps, intake parts, exhaust manifolds, driveshafts, rudders (if different from standard inboard parts), computers..
I plan on purchasing a few more spares before the end of the year. If you get a good deal on a Toyota vs another boat, put the money into a few parts from the website.
I love my Epic, not selling anytime soon, it will outlive me.