I love your profile picture of Tookie, he is so adorable! You did such a wonderful thing by giving him a new home. Good for you!

It always makes me incredibly happy to hear when people adopt birds. I got my GCC from Craigslist, too! He came "free with a cage"---the title of the ad was just about the cage, I honestly don't even know why I clicked on it, but I did, and it was a description of the cage but the very last line was "also comes with a green cheek conure." LOL
I e-mailed the woman about it and didn't hear back from her for three weeks so I had given up by the time she responded and was surprised to hear he was still available. It turns out she knew it was best for him to go to another home (she didn't have time for him and he spent most of his time in his cage) but she loved him and was having a hard time parting with him and that's why she didn't respond for so long.
I am a really big fan of GCCs, I had no idea what they were like when I adopted Bubba but they are so full of personality. I love Bubba to pieces and I am so glad I found him on Craigslist; he is just a giant ball of cuddles. He is so happy all the time. He has a great attitude. If I am having a bad day he cheers me up so much with his clownish ways and his super happy whistles and dances. He is always really eager to do the tricks he knows so he can get some treats. If it was up to him he would cuddle and get head scratches all day long.
He wasn't like that at first and was very bitey with my husband but with time and positive reinforcement he turned out to be a wonderful bird. My husband is actually his favorite now, he will cuddle with me but if my husband is around he'd rather cuddle with my husband.

I know yours will come around as well, especially if you use clicker training, that's a very effective way to build trust and you get good results pretty quickly.

Excellent advice from friend2parrots. It's very important to avoid bites so it doesn't become a habit, give him some space, and do some clicker and target training with him as it builds trust and is a great way to bond with your bird and just have some fun together!
I also agree with friend2parrots 100% on allowing his wings to grow out because that has a radical effect on a bird's personality. My GCC loves to fly; he follows me all over the house, up and down the stairs, all day long. I also do a lot of flight recall with him. It's beautiful to watch him and I get a lot of joy out of seeing him in flight. It also helps him stay in shape and gives him an outlet for all his energy because GCCs in particular are really busy, energetic birds.
Re-homing is traumatic for a bird, even if they are going from a bad environment to a better one. Tookie will be cautious and defensive for a little while---especially if he is used to being bullied---but if you give him time and are patient with him he will settle in.
As far as changing his name... I have a rescue and a re-home and I just kept both of their names and it wasn't a problem. Neither one of them said their name when I adopted them but they both say their names now.