I wholeheartedly agree with toastii on the anemone. I'd strongly recommend against putting one in a tank that's been established for less than 6 months. I'd also recommend against getting one before you yourself have had at least 1 year in the hobby.
Please don't take this as a slam, but I think you need to slow down. You're tank should be completely empty for 2-3 weeks minimum if this is your first one. Even if you're experienced, I don't think you can tell much about how stable a tank is unless you've been observing it for at least a couple weeks. I wouldn't worry about getting nitrates down to 0, but less than 20 is a good goal. Nitrites should be at or very close to 0, and ammonia should definitely be undetectable. Once you've had these levels for 2 weeks, then it's time for your hermit crabs and snails. They're actually more sensitive to water conditions than fish, but they're cheaper, so no one cries when they lose $5 worth of snails and crabs. They should be just fine, though, if you've done things right. After a couple weeks with just your cleanup crew, if things are still looking good, try a fish. . .just one fish, not seven. With biological filtration, you need to increase livestock slowly or you'll overload the system.
Hope this helps, and if you can find another LFS, you'll probably be better off. Petland is notorious for just being a clearinghouse for fish. Their staff usually has limited knowledge on the marine life in their care, and they're generally just trying to make a sale. This is certainly not true for all Petlands, but it seems to be the case for many.
Here's what you're doing right, though. You're asking questions. Take them all with a grain of salt, but the nice thing about these forums is that people usually don't have ulterior motives, and they're genuinely trying to help you make the best decisions.