Machine Age, a Duopar removal tip that might be useful to you whether you keep the derailleur or trade it: the little plastic cover over the derailleur mounting bolt is quite fragile. If you try to pry it off from the front with a screwdriver, it will probably break. I've seen that happen twice. I won't elaborate on the circumstances.
The right way to get the cover off is to stick a small allen wrench or something like it into the mounting hole in the back (with the wheel removed). That will neatly push out the little plastic stem that fits snugly into the mounting-bolt hole to hold the cover in place.