Don't let that feeling of being rich get to you - remember that the money has to last you until January and don't blow it all at once. I've seen new students do that and then they're lining up at food banks by November and in some cases can't pay their rent.
Wait to buy your textbooks until after the first week of classes, you can always preview the first chapters on places like Google Books or the publisher's website if you want to get a head start but professors will sometimes change their minds about a book by the time school starts up and it sucks to waste money on a book you didn't need!
Give it a few days and the website will tell you when your funding will be released. They are crazy backlogged this time of year getting everyone's applications and entitlements sorted so not everybody gets the same messages at the same time.
I know it's stressful not having access to it yet but it will come. Just breathe and enjoy the last couple weeks of summer!