Rachel,
These guys knows what they are talking about...
I was a total newbie in aquarium hobby 4 months ago, and went through the same debates at that time - getting different advices from LFS vs the forums like this one. In my case, I decided to follow the forum advices, and I have yet to loose any fish due to any human mistakes. (Well, lost one but at least I know the exact reason why I lost it). In fact, my confidence grew during the past two months to the point where I changed my tank plan and started adding more sensitive fishes. Despite this, all fishes are healthy and I am confident that they will continue to do so...
During the past few months, I was "testing" the advices from the LFS by playing stupid to see what their responses are, and in just about all cases, they clearly know less than what you can pick up in these forums in few months... Just looking at the fact that two different LFS sales people giving me two different advices on the same topics says alot!

You will eventually notice that most of the sales people simply don't care as much about your fishes as the people who exchange messages here...
Simple example:
- Me: Eh, you have two types of algae eaters here. Which do you recomend? (They had oto and false SAE, which they don't realize they do)
- LFS: What types of algae do you have?
- MS: Both brown and green. Some hair algae as well.
- LFS: Buy three of each. (Notice, they didn't even ask my tank size!)
- Me: Ok. I'll try out just one of them first. (Walked out with 3 Otos only).
You won't regret it by following the advices from these forums...
(message from a newbie to a newbie...

)