I have very old Pella Wood interior casement windows where the sashes are starting to sag. I want to replace them with a vinyl casement window, but I don't know how to get rid of the old hardware in order to put in a vinyl casement window. I have vinyl siding with j-channel applied to the siding. Can you please tell me the best way to get rid of the old window and be able to put the new vinyl window in?

I use a Sawsall or reciprocating saw to cut alone the 4 sides. Use ablade made for wood and metal.

Are you saying use a sawsall and cut the nailing fin from the outside, take the nails or screws out of the frame and pull the window out?

Pretty much. The window is just slightly smaller than the opening and was shimmed and mechanically attached with nails or screws. I could spend hours trying to pull nails but they are often hidden so cutting around the window with a reciprocating saw is quicker. It would be another matter if you plan to reuse these windows eslewhere.