Two questions




Thanks for posting! Removing your casement operator may prove to be a bit difficult since the handle won't spin, unfortunately. You will have to do your best to open the window by hand. Once you have, the screws should be accessible on the other side of the sill trim.
If you cannot get the window open at all, you may need to hire a contractor or a professional to come open the window for you. Then we can assist with recommending the replacement hardware with a few photos of the entire assembly.
I'll need to see a photo of the body of the operator as well as the arm(s) and how the operator attaches to the bottom of the swinging sash (window).
Please let me know if you have any questions in the meantime.