I thought that too at one time, but once your tank is cycled and you're in a routine of regular water changes and the fish start thriving, it'll look different to you.
When you get dechlorinator tomorrow, get some Seachem Prime (first choice) or StressCoat (second choice) as this conditions the water as well.
The guy at the shop is an idiot ... there's hardly a way you can do too many water changes. Too few, yes. Too many? Doubtful.
And when you're testing your water, please make sure you follow the instructions to the letter. Shake the bottles as long as it recommends, even longer.