I cannot answer if you need to use a certain (perhaps approved?) translator for these purposes, but if you need a translator, PM me and I can give you the details of another member on this forum who recently helped me out with translations and was very reasonably priced but more importantly, excellent and extremely efficient and quick.

As far as I know there is no list, unless it is special to your canton. Our translator stamped our translations with her business stamp and that seemed to be fine. If extra "officialness" was wanted you would have been asked to get the copies certified by a notary. I can't see why there would be objections to an out-of-canton translator -- consider that for some less common languages there would certainly not be a translator available in every canton.