I find the best way to deal with the anxiety of calling is to call asap to get it behind you. The same goes when setting up an appt. Your anxiety may very well make you want to put it off a couple weeks to give yourself prep time, but I want to encourage you to make the appointment date asap as well. The less time between now and the appt the better.

The others are spot on about what to expect when you get there, so I won't bother repeating it

Best wishes and good luck!!!