Bob,
You can definitely cook ahead. When I do that, I go ahead and pull, just like I'm going to serve it then, then get it into vacuum bags pretty quick (if you have that option). If not, put the pulled meat in big Ziplocs and try to get as much air out as possible. The meat will retain the moisture if you get it sealed pretty quick.
When you reheat, just put a little water in the bottom of a pan or crock pot, put the shredded pork in, and heat it up. It comes out just like the day you cooked it!