Instead of replacing the hinge pins, I usually cheat and do it the easy way. I take the bolts loose on the bottom part of the door where the hinge bolts up, and put washers in there to shim it up. I have tried to loosen the bolts on the cab, that would let you raise the door the proper way, but they are terrible to get to, and after I broke a ratchet trying to get them loose, I just used the washer method.
After you get the door lined up, if you still have to slam it, and sometimes it bounces back and doesn't close all the way, check the striker pin on the cab. It should have a plastic bushing around it. If it's just bare metal, get some of that PEX plastic plumbing line, cut a short piece to fit, and the slit it lengthwise and snap it onto the pin. This really makes the door shut nice if this bushing is missing.