It's funny, how even though there are more and more parks popping up everyday, they are still thick as pea soup, as soon as school gets out. I have seenj skaters, bladders, bikers, and scooters all end up in a crumpled heap. Some are okay, some go to the hospital, but I have never heard anything about a lawsuit. The little kids are notorious for not looking before they leap, which is why they are usually the victims of the collision. At worst I would think you might have to deal with an overzealous parent, or maybe bring a kid to the hospital.
Nobody goes looking for a collision, and remember- accidents happen.
Removing a busted kingpin is one of the most annoying things to do. The way I do it is to find something that will go under the baseplate, but not covering the head of the kingpin. Fro there, just hammer it out. It may take a while, so be ready. Next, just put the new one in, flip the baseplate over, and hammer it back into place.