[C#] Still a bit of a noob - can anyone help me fix my disaster of a project?

Project gist: “Reddit Couriers” visit customers to pickup and deliver parcels around America. They need to maintain a list of all the visits that they make. Each visit has a customer name, customer address and arrival time. Pickups also have a delivery name and a delivery address. Users should be able to view a summary list of all pickups/deliveries as well as lists solely containing deliveries or pickups. They should also be able to add new pickups/deliveries, and edit and delete existing pickups/deliveries. Data should also be saved to an xml file upon clicking the save button, and should be loaded upon startup.

I've been trying to get this to work for hours - at first it didn't read/display the xml at all, now it gives errors about random things and won't run at all. The more I try to fix it, the more messy it gets. Can someone please help me fix this?

Project code can be seen here.