I'm really excited about seeing all the Halloween stuff!!! I was at DLRP last October, just before Halloween season began, and it was brill! Most of the Halloween decorations are in Frontierland (renamed Halloweenland for the season) but there are Pumpkin men and ghosts on Main St USA, and there is a Villains show near the Castle every day. They don't, as far as I'm aware, decorate the Castle.
The OUAD is the same as out of Halloween season. But 20 minutes before that parade, there is a Halloween pre-parade, on the same parade route. Thats where you see Jack and Sally, pumpkin men, and villain characters parading.