... a ten gallon isnt that big really. And realistically, a 5.5 gallon will work, if its a male and has a minimalist set up. A Large Exo Terra Breeder Box or Large Faunarium will also work.
A simple 5.5 inch heat reflector lamp with a 25 to 40 watt red bulb (such as a party light) will adequately heat the enclosure. They do need heat, unless your room is about 78 to 82 degrees...So that was pretty misleading of the pet store employee, you should call them and complain.
Theres a care sheet on the site, but heres what I have to say

Enclosure; plastic containers are generally better because they are light weight and easy to clean. The above mentioned large sized plastic terrarium will work, and so will a 16 qt plastic shoe box like you can get at walmart or the dollar store and melt or drill some holes in it for air. Aquariums are heavy, and the enclosure will need to be completely cleaned frequently.

There are two general methods for substrate; you can use coco fiber soil and you can use moss (you just dont want them to ingest any) and this will need to be changed frequently. Coco fiber and moss can be spot cleaned for poop, and dirty moss has the advantage that it be rinsed, dried and reused a few times before it breaks down.
The other method is to get a sheet of aquarium filter wool, or a filter sponge that is about.75 inches or an inch thick or so and place it on the bottom of the terrarium and then place water in it just up to the top of the filter mat. Thats how the asian keepers do it and this is where a plastic container makes it easy, because you want to change the water, rinse the filter pad and scrub the container with a wet sponge (one used only for this, with no cleaners) and simply replace the (treated) water.

If you use moss or coco fiber (not coco husk!) they really dont need a hide, but they will need a small water dish, like a terra cotta saucer which needs to be changed daily. If kept on the wool mat with water, if it is a nervous frog, it may need a little hide, either plastic or curved cork bark cave.

If you use the wool mat and water set up, a small heating pad can be placed under the terrarium, but make sure the terrarium has feet, so hot air can escape and not build up underneath. Otherwise, place it on the side or they will burrow down and cook on top of the heater. I prefer a heat lamp suspended above the terrarium, clamped on to something. Get a small thermometer to keep watch on the temps. Use a low watt red bulb. The plastic containers also hold heat and humidity better than a ten gallon does.

FOOD! The frog ingesting moss or gravel while eating does present a compaction risk, more so with gravel than moss. I dont recommend just tossing crickets into the cage and letting the frog have a go at them. The first major reason is that any supplement powders on the crickets may rub off before the frog eats them, they may drown, chew on the frog or hide in the substrate. The Frog also may ingest quite a bit of substrate when lunging for crickets as well, and this even proves a risk with coco fiber. It is far better to feed with a small pair of feeding tongs, you can get a cheap plastic tweezer at the walgreens that will work just fine, or at a pet store.
DONT feed goldfish, as they are very dirty. Mollys and Platys would be better, but even then there is a risk of them harboring dangerous parasites and diseases from the fisheries they are hatched in. You can raise your own feeder fish or make a bait trap and catch minnows if you live near a lake or river. Pinky mice should be fed sparingly and dipped in Calcium/D3 powder, they are high in fat. A full grown frog can eat a full grown mouse, but this should be once only every month or so. Crickets are fine as long as they are "gut loaded."
A plus is that because they are easy to tong feed, you can use canned crickets as food. I would also recommend buying a bag of Samurai Pacman food. Its a powder you add water to and roll into a gummy ball and its a great food. Between that and canned crickets, you dont even have to mess with live foods.
Another great staple food that is easy and convenient is NIGHTCRAWLERS. You can find them at walmart even, they are cheap and great food for a frog. Make sure they arent died or scented.
Under two inches, feed day or twos, over two inches second or every third day, and when full grown, once or twice a week.

Day time temps need to be between 78 and 84 F. Nighttime they can drop down to 72. Mist daily, but dont make the substrate soggy.

Not a difficult pet as long as you keep them warm enough, their enviroment clean, and you dont over feed them.
They dont need special lighting, they dont need a large enclosure, they dont need live crickets.

Dont feel bad, my first pacman frog was an impulse buy and the employee that sold it to me was just as misleading.