Casement window operator stripped
We may very well have a replacement for this operator, but I unfortunately can't determine the best option from these photos. Would it be possible to see a clearer photo of the arms that open and close the sash? I can see one of them partially in your first photo, but seeing the arms in one shot in their entirety would be the most helpful. Please let me know if that would be possible!
Thank you! That's a huge help. Based on this photo, my top recommendation would be the 39-083. I think this may be what you need but look it over and see what you think. As long as the "elbow-to-elbow" dimension, measured while the arms are closed, is the same at 21-1/2" then I am confident that this product will repair your window.
You say your operator knurled is stripped. Try turning it using a set of pliers or vise grip-type pliers to open your window. Also while turning it try pushing the window open with your hand. Just don't push too hard and don't press on the glass. Lastly, even with the window closed you should be able to gently pry up the wood sill cover to access the mounting screws.
No, you won't be able to disassemble the operator base. If you aren't able to physically push open the window then something might be stuck. You could try prying off the sill cover like I suggested. Otherwise, you may want to seek the help of a local professional to come out and do the project for you. It may require some hands-on experimentation.