K.E.
I would check out the forums on welltrainedmind.com. Even if you don't go with the classical model, these women have a wealth of information and great opinions on the different curriculum available to homeschoolers. I have also found great reviews on curriculum at homeschoolreviews.com. There is so much information out there.
I also recommend reading So Your Thinking of Homeschooling by Lisa Whelchel. It has a nice brief overview on the methods that you can use to homeschool.
I wish you all the best in your exciting journey. I don't have any experience with taking a child out of school, but I think January would be a great time to pull your DS out of school. This will give you time to reserach / select & purchase curriculum and will give your DS some time to prepare for the change. I have read that some people allow their children to go through a "deschooling" period so if you wanted to do this you could kind of gradually ease yourself into homeschooling and try and be where you want to be when your school year starts next year (which can be whenever you want it to be).