There is only one legal way to remove the refrigerant, and that is to recover it into a cylinder. You're supposed to recover to a 4" vacuum or more.

Yes you do have to pull a vacuum on the system before you charge it with refrigerant. You get a vacuum pump. I've heard that some Auto Zone stores lend them out, but I bought one for about $200.

You will also need to add oil to the new dryer before you install it. And don't uncap the new dryer until you are ready to add oil, bolt it into the system and pull a vacuum right away.