sterilise and deworming

hey there...my kitten seem to have pot-bellied stomach and it is also kinda hard...i tink that there are worms in it..but wen i went to a pet store @ serangoon, the person said that if the kitten is less than 6 weeks/months..im not even sure my kittens ages..niwae do u guys noe the price of deworming at the vet??and sterilise too?i nid information on this..as im not familiar with this at all!! THANK YOU!!