Update!
I got the driver's side liner on, but the back part that's held with the self-tapping screws is now without the clips that the screws screw into (due to Dad and me brutally murdering them while pulling the old one off). I don't know where to get these clips or how to install them once I have them because they have a washer-shaped head that fits between the fender and the exterior plastic cladding, then a square plastic peg that sticks through the wheel well liner.
I know, we shouldn't have killed the plastic clips on that part, but I didn't know they were what the old liner was hooked on. I assumed that some rocks had gotten wedged in along with the entire handful of dead leaves I found in there or something

"If you don't love me at my diddliest, you don't deserve me at my doodliest." - User ktluvscricket of reddit