We're new into the hobby, and fortunately we knew the more research you do before stepping foot in the lfs the better! I understand that in my area this is a very niche business and since we don't have any saltwater bodies around it can be hard to gain the knowledge. There are a couple of stores that don't give necessarily "bad" information, but are more out to make a sale than educate the customer.
I can speak from experience, because I have a family owned business myself that is in livestock as well (exotic birds). We aren't out to sell someone more than they need, and definitely won't sell them something more than they can handle. It is absolutely unforgivable for a shop selling livestock to give out bad information that may kill the livestock they sell. Now we love our business and love the animals we keep, so there is more sentimental value with us than at your regular national chain store. What do you expect when they employ 16 year olds for minimum wage? I see all the time that these younger workers are not being trained properly. But how can you blame them? One of the national chains here doesn't carry squat for saltwater. They have maybe 3 or 4 tanks of some damsels and percs, but not really much else. And with the inventories they keep, you can't expect the employees to know everything about everything. I have more respect for someone who admits they do not know the answer than someone that makes it up as he goes.
All in all with my longwinded post, do your own research and don't take everything the lfs says as fact. Mistakes will be made, you just have to learn from them.