Its totally easy ... once you enter the immigration area watch all the way to left and you'll see a small counter who will check your USA Visa and will give you a small paper which you can show to the immigration officer.. it hardly takes 5-10 minutes.. your passport wont be stamped with visa in it but on a paper.. charges are 120 AED ( roughly 2500 rs ) and you can pay either byAED or Cards also. Dont worry
The best option, if you are visiting Dubai and your stay would be for 2-3 days, is to travel to another country and take a Transit Visa to Dubai ! This is the latest update where for 2-3 days you can see Dubai on a Transit Visa. It is also extendable.