Welcome to the world of teaching! You'll find so many great ideas here on ProTeacher, so you're off to a great start.
There's nothing wrong with asking the administration. If you've officially been given the job, then it's normal to want to see the room. If she doesn't want you to have the keys (we don't get them over the summer, so schools are different), you can still ask to see your room long enough to make measurements and take pictures so you can start planning on paper.
Does your district have a pacing guide? If not, I'd start planning by mapping out the year to see how much you have to cover. If you can talk to another teacher in your grade level, you can get a lot of help. She may even offer to let you see her lessons to get an idea.
I hope you have a great year!
