Luke
One of the reasons I recommend visiting a store is to get a handle on how big scopes actually are. A 12" solid tube dob is about the size of a small water heater, and then there is the base. That is not to say it is too big for you, just it is a load to handle if you are expecting something smaller!
With collimation a laser is not a bad idea, but there is more to collimation than a laser. A good guide to collimation without a laser is here
http://www.astro-baby.com/collimatio...on%20guide.htm . If you follow this procedure it will setup the scope and you can then use a laser to tweak it each time you take it out.
As with many other things in the world of lasers you get what you pay for! I had a similar laser to the Seben one and have recently upgraded to a Howie Glatter. Bit exxy but much better made and really accurate.
Cheers
Malcolm