When you first started up the Nexus 7, did you sign in with your Google account?
Go to Settings/Accounts-Google. Do you see your Google account address listed there? If not, then you're not linked to your Google account. If you do see it, tap it and look at all of your Google aps. Make sure that the ones you want to have synced are checked.
Also make sure that your Background Sync is on. This is most easily done by placing the Power Control widget (in your Widgets list) onto a homescreen and tapping the Sync button (the circular arrow) to toggle on or off.
As for all of the apps you may have installed from Google Play--they won't auto-install for you. You'll need to download and install them yourself. Go to Google Play, tap the My Apps icon at the upper right, then tap All in the upper left, and you'll see a list of all the apps you've ever installed using your Google account. Tap the ones you want and install them.