My 6 year old boy is the joy in my life, I adore him! He is also a rescued former racer. My advice:
As others have said, be patient! Racing greyhounds have had a pretty awful start in life. They don't know how to be pets. Even if she is settled into the rescue centre when you bring her home she will need time to adjust and settle again. Patience is the key.
Be prepared for some separation anxiety, especially at first. Because of the above, it's natural to have some anxiety. But also they are known as velcro dogs, they just want to be with you all of the time. Mine has never got over it and cannot cope being home alone for more than an hour - I have a local teenage neighbour who I pay to babysit if I'm out for the evening. My neighbour also has a grey who stays home alone for 4-5 hours fine.
Get a really big sofa. You might think you don't want her on the sofa, you'll change your mind. 
They give the best cuddles, but they can also adopt all sorts of wacky poses. I could compile a yoga manual of pictures of mine.
Despite being racing dogs they don't need too much exercise. Mine can walk about an hour and then he's had enough, generally prefers half an hour walks twice a day. But every so often we go to a fenced-off green and he goes crazy running at full speed, he loves that once in a while.
Food - they'll give you her specific dietary needs when you take her home. But just be careful not to eat too close to exercise.
Greyhounds are the most wonderful pets!