I'd say the water change thing depends on whether or not your live rock is cured or uncured. If it's cured when purchased your good without too many water changes. I've seen some uncured stuff, however, that would turn the tank water into sewage if you put 50-60 lbs in. With this stuff you'll need to do the water changes if you want to keep the life in the live rock.

unmeg's right about salt being costly. Do yourself a favor and order one of the big buckets. Always be sure to keep enough salt for at least a 50%(100% is better) water change on hand. You never know when you'll have to do an emergency water change and salt's a bitch to find in the middle of the night.