Yep K= Kelvin. It's a temperature rating. =] White light is somewhere around 2,000 K or something.
You'll want a CFL. =] One of the swirly bulbs. They use less energy and are better for aquariums because they don't get as hot so they wont really affect the temperature.
All of the plants I listed earlier are stem plants. =]
If you want free stem plants you could look through a planted tank forum such as www.plantedtank.net
They normally have a sales subforum. I know on The Planted Tank you can only see it if you're a member. It's called the Swap n' Shop! =]
You'd probably still have to pay shippping but that's it. =]