Welcome, welcome! Along with all the good advice the above members have given to you, I would recommend (sadly) that you not go by LFS advice in the future - their job is generally to sell you fish and supplies - whether or not you need those supplies and whether or not the fish will get along or outgrow the tank you purchase.

Reading material here on the forum (especially on cycling a tank) will help a lot and asking advice before making another fish purchase!