I'm sorry this happened. When I had a small pet cremated, it was 45$, plus the cost of an urn(that's optional though). The costs go up according to how big the animal was, at least here they do.

There are things you can add to the soil to cover the scent. My neighbors have covered their dogs' graves with large rocks, not one rock, lots of them...marks the spot, makes a nice place for them to remember at and prevents any digging by other animals.