Hi and welcome to the forum. I am not certain whether to congratulate you on your new friend of not. I don't ever gift someone with a live animal at least until I have talked it over with them to be sure that they know how to care for it and want it or not, otherwise even though they may mean well it is rather rude to give an animal to someone. While I am sure your sister meant well and it does sound as if you might want this bird, I am not really for gifting people with animals.
Any way the first thing that I think that you need to know is what is safe or not for your new bird as the diet that you described was fairly common 2o to 25 years ago, but was really not good for them, so here is a link to foods and things that are safe and toxic to parrots, the actual list is on page two of the topic.
viewtopic.php?f=8&t=12521 Like with many parrots that like to be touched, one of our biggest mistakes with them is to pet and scratch their entire bodies. This is not a good thing to do with them as every where on a bird except for the feet, beak, head and neck is an erogeneous zone and although they love it, it causes them to produce sexual hormones and then you end up with an aggressive, overly hormonal and sexually frustrated bird. While this is bad and with a smaller bird can be rather painful to you, with a bird of the size of a cockatoo armed with the very large and strong beak it can be quite dangerous. This is not the birds fault, but one needs to be aware of this and conduct their interactions with the bird accordingly.
Just as with many other parrot species, cockatoos bond deeply with their chosen human and just like the other parrots they can be quite jealous and protective of their human as they see them as their mates and not just any flock member. If cared for properly and treated respectfully Cockatoos can be extremely wonderful companions.
I don't have any cockatoos and think that other than just general information, we are better to allow those with more experience than I have to take this from here.