First time....

My husband and i were told that he couldn't have children. Well , after we decided to give up for awhile and come back to it later, I found out we were pregnant! It's our first child and I have no clue what to expect. My first appointment is on the 20th of this month. What do they usually do during a first check? Should I be as nervous as I am? We are still in a shocked disbelief. Will they do an ultrasound then or will I have to wait? Will I get a different due date or a better idea of length of time of how far along I am?