Hi and welcome to the Forum!! Congratulations on your purchase of Stoli..
I think you will find this forum and this site to be one of the most comprehensive. Joe Heinen has done a wonderful job providing some of the best information out there. Also check out Julie Maguire's site at Long Island Turtle Rescue (you can find the link on the main page herein -- scroll down)
Most pet shops are do give out the wrong information. The best thing is to follow the caresheet on this site and the list of appropriate foods. In terms of the greens you mentioned, those sound fine, you must want to make sure your Stoli is fed a good variety.
Pellets are definitely out for many reasons and it sounds like you are now aware of that

Keep in mind that fruit is not appropriate as it can change the flora in the gut and encourage parasite growth. The only fruit that is safe is cactus pear from the Opuntia cactus. Unfortunately this is seasonal and the window of opportunity to find this is quite narrow. However, you may want to consider checking out Joe Heinen's Carolina Pet Supply. He carries many wonderful products including powders that are all natural and are very healthy as a dietary supplement. He and his wife, Karen are also very helpful in answering any questions you may have about any of the products. The prices are reasonable and they are very trustworthy.
If I sound like a commercial advertisement it is only because I think very highly of Joe, the service he provides to all of us and his store. I have only been a member of this group since February, but I can tell you that you will not find a nicer and more caring group of folks.
Glad you are part of this now. Good luck with Stoli. I hope this note has been helpful
Donna