So ask them how much for a new rear derailleur, bigger cassette, and new chain. See if you want to spend the money. Nothing wrong with going that route. Get an 11-34. As you get stronger, you can change to a smaller cassette if you want. You'll notice that the gears are further apart with a larger cassette, but you'll be able to spin decently on hills without blowing up. It's supposed to be fun. A lot of the folks I ride with have that cassette.
A small cassette is a status symbol. It says, "I'm strong!" The more money one pays for a road bike, the smaller the cassette is.