Dang! I wish it were as simple for you as it turned out to be for me.
I haven’t replaced a potentiometer, but I have opened my Pyramid and made a modification (the very early models needed to have a couple of resistors removed for better 1v/Oct performance) and while I was super nervous about it (SMD components, and my precious sequencer!) @squarpadmin via email were very supportive, and supplied great instructions and it was a snap!
I just bet if you write to them they’ll give you similar instructions for replacing the pot, and may even have some other ideas. Second hand or no, it’s a Squarp Instrument and they’ve got your back for sure.