Actually, you might do a search because this has been discussed a fair amount recently--apparently quite a few people are going at the same time this year!
First of all, the first weekend in October is not only the opening of Haunted Mansion Holiday, it is also Gay Days, so expect heavier crowds. This means that you might want to be sure to get your hotel reservations early, especially if you intend to stay onsite--Paradise Pier traditionally sells completely out this weekend. Also, you'll want PS at any restaurants you intend to eat at--though this is a good idea at any time of year, it never hurts to have a reservation.
I don't have experience at DL the first week in October, but I'm usually there the last week in September, and the crowds are usually fairly light. Last year we did use FP, but we never stood in line more than 20 minutes. Crowds make me antsy, but I had a great time, so the crowds last year couldn't have been too bad.
For hours, I usually check the park update at mouseplanet.com. They have archives which allow you to check previous years, so you can kind of get an idea of what to expect. Hours will be shorter--I believe that DCA closes at 6pm. This is also great for getting an idea of what rides will be down for refurbishment, though with the 50th anniversary I'm hearing that they don't want rides to be down if they can help it. You can check what parades ran at this time last year. I do know that they ran the Electric Light Parade on the Sunday that we arrived. The rumors I'm hearing say that they're going to try to have the parades and fireworks during the week even in the off-season for the 50th, but it's just a rumor, so take it with a grain of salt.
