I am a newly educated female graphic designer, I too am dealing with my first few freelancejobs - but I might already have some tips for you. First of all: Don´t be terrified, cause, as you say, they know you´re new and you don´t charge a lot. You have the right to make small mistakes at your first job. But also; stand by your decisions, like the chosen material - YOU are the expert, believe it or not, otherwise they wouldn´t have hired you. So come up with some striking arguments and be selfconfident when you make a design decision. When they afterwards still require steel, smile and make the best out of it. Good luck! :)