I replaced my own hybrid battery, and you should strongly consider doing the same. Physically swapping the batteries is easy but time-consuming, as you'll probably have to take the rear seats and other parts out to get at the battery.
http://ecomodder.com/forum/showthrea...ems-13610.html
If the '07 battery was in good condition when parked, then all you need to do is rebalance that battery, giving it a good, long soak on a grid charger BEFORE you drive with it. If you skip this step, you will need to take your battery apart and refurbish it in a few months or a year, using the cells in your other pack as spares.
If you decide not to DIY, there's also Hybrid-Battery-Repair.com, who does it for less than half the price of the dealer. He also buys failed battery packs, such as your old one.