You can book a package in Oct (the rates for 2010 should be out then) and only need to pay a $200 deposit. Then the final payment is due 45 days before travel. If you do room only, you have to pay the equivalent of 1 nights stay, but would have to switch the ressie over to a package, and get a refund of the deposit & put another deposit of $200. It's easier to just book the package, IMO.
Plus, once you book you can keep your eye out for deals that may come out, and then call and have that special (or if you get a PIN code) applied to your ressie, and save yourself some money!
TA's can often help you plan & book your trip, and shouldn't charge you extra for their services (if they do, don't use them! they are paid by Disney). Plus, a TA will keep an eye out for a deal, so you won't have to (unless you receive the pin code, then you will want to call your TA and let them know to see about getting it applied to your ressie). If you use a TA, they have to be the ones to call Disney concerning your ressie. They will also make your ADR's, unless it is something you want to do on your own.