Orchard grass is fine - it's one of my bunnies favorites
They can have any type of grass hay, which includes types like Orchard grass, Timothy, Brome, and Bermuda grass. Timothy is the most popular kind to feed rabbits, but I like to make mixes for my rabbits made of at least a couple of the different types of grass hays. It gives them a nice verity and makes foraging for the perfect pieces of hay more interesting for them.
Do a google search for "NIC rabbit cage". NIC stands for "Neat idea cubes". They are sold in places like Wal*mart and Target for like $15 a box and you can make a nice big custom cage with them.
I don't usually ever recommend any pet store type rabbit cages. They are usually too small and overpriced. If you don't like the idea of using NIC's to make a cage, you could also look into using an Xpen or a large dog crate. Especially since you don't know what type she is and if she's full grown or not - get the biggest cage you can.
You might want to take it easy on the greens for now. If her tummy isn't use to them they can cause some problems - feed them in moderation, especially at first until you make sure she can handle them without any problems. I also use and recommend Oxbow pellets if you can find them.
Congrats on your new addition! Any name ideas yet? She's very lucky to have found a good home.