I have 500 domains, want to buy one?
GoDaddy is pretty good, though I use moniker.com for most of my names. DO NOT use network solutions, or even search for the name with them. Once you search a name, they "reserve it" for 3 days which means you have to buy it from them or nobody for the next 72 hours.
stick with .com even if what you want is taken, .net / .us are a big step down credibility-wise.
probably not, since you would be registering it in bad faith though you might have an out because you weren't trying to profit from it. I wouldn't go near it with a ten foot pole.