The amount of light you need depends on the square footage of the area you want to use. A 400 watter is a good start but good results can be had with less.

Expect to get about 1oz dry from one plant in a 1 gallon pot. Yield depends on many factors though.

No, you're not an idiot. Just make sure to take care of odor control.

It's pretty safe ordering over the internet. I've only ever ordered from SeedBoutique (formerly Seedsdirect) and always got good service.