I wanted to do the opposite (hammer to adze) and was told I just had to buy the adze separately but that it was no problem. In the end, I decided I was fine with two hammers, though, so I didn't investigate any further.
At the back of the tool, there is a big screw that you can loosen to replace the hammer/adze, just like you do for the pick. It takes 5 seconds.
Oh, and you are going to love those tools