You do need a physical and a drug test
The main difference between the licenses is the amount of time you can document on what size vessels and where it is (offshore, near shore, inland). The test is the same. There is a really good book by a guy named Charlie Wing that will tell you all you need to know and has every test question in it. There is also a testing program on CD rom that you can practice on.
I got mine at Boat US....so you better hurry