I know how hard it can be when you go into a pet store, while some of us here go a little over board with adoption because some/most SPCAs do not have a no kill policy, but in saying that I used to work at a pet store and as a sales person I knew what to say to get someone to take a pet. NOW, also in saying that I was one a the rare people that spend hours talking to possible new pet owners to make sure that they where ready for their new pet. I did end up quiting because of many reasons one being that my fellow workers did not have the same views on people buying pets and making sure that they where ready for them.
My advice is that if you are easily temped to buy from a store, just don't go in. If your at home ask your parents to go get the food, hay and so on without you so you aren't temped. IF you are not at home ask you other half or a friend to help you out and tell them you are always temped to buy other pets, I'm sure they will undestand.
As for the pet stores comment on fresh foods, as you can tell from everyones posts that was miss information. You MUST give them fresh foods but always check what they can have and how much. Carrots if given too much can cause problems with I believe the liver due to the Vitamin A. too much lettace can cause diarriah because of how much water it has, and by too much I mean a head of lettace per piggie per day. In reality anything good can be a bad thing if you give too much, accept hay and pellets. Always do your reseach as this site has many wonderful people to help you out.
Now people can bash my post all they want as everyone has their own opinion and this is just my view on things.