Two things:
That is a picture. I'm not sure why you can't see it, but you can try: https://goo.gl/photos/LmPT71zcsLb4E1X76.
However, it doesn't matter because:
This is the first mod I've needed Module Manager for. This is no doubt a noobie mistake that will have you rolling your eyes, but every other mod I've tried (not many) worked fine without it. What I ended up doing was downloading CKAN, and using that to install both the Part Overhauls mod and Module Manager. Problem solved - full part replacement seems to be working. Thanks for your patience.
One final question: The new stock parts are backwards compatible, but I'm guessing the other ones like "pug" and the shelled versions of the stock parts are not?