You will love the WSM. They are great smokers, and there are a lot of folks here with them so advise is just a mouse click or two away
If you don't already have one, I strongly suggest you get a charcoal chimney for starting your coals. Home Depot or Lowes should have them (get the Weber brand as some of the imitations are not going to hold up - my original Weber chimney has been rocking on for over 6 years and is still rock solid). I would also get either a metal pan or one of the fireproof concrete mats if you are going to use it on a wooden deck. Here is a photo of my WSM and chimney from it's first fire in 2005. That is a aluminum water heater pan under the WSM. I now have a concrete grill mat (looks much better, as does the new deck that replaced that one).
There is also another website dedicated to the Weber smokers called "The Virtual Weber Bullet Bulletin Board", with tons of info on the WSM, modifications, etc... These smokers have a huge following and are built to last (as are most things made by Weber).