Hi and welcome to TN!
I don't know a whole lot about that engine in particular, but I do know that the Toyota Vista Ardeo was only imported to European and Japanese markets. Perhaps this is why only very few people own them. The 3S-FSE is just a 3S-FE but with Direct Injection meaning it burns very efficiently. Toyota didn't make them for very long, but if the reliability of 3S-FE is anything to go by then I'd say you have nothing to worry about.
This type of engine was also used in the Corona Premio, and a few other vehicles that Toyota produced. As for things to be aware of - The 3S-FSE D4 had an injection gumming problem, but they managed to sort it out when they launched the current direct injection engine, the 1AZ-FSE. So that's something to keep in mind. Might pay to pull them out and check them.
I hope that has helped you in some way, and wish you all the best in finding more info.
I hope you enjoy yourself here on the forums