For your 3G problems, try doing a reset, no data loss, it's just like restarting your computer.
Hold down the home/sleep button together until you see the apple logo and then release, then wait for your phone to boot back up.
If you're still having issues with imessage take a look at this link http://support.apple.com/kb/ts2755
If that link doesn't help and your still having issues with 3G then you will need to contact your cell provider.
Apps & music should be in your itunes, see this link to sync them back http://support.apple.com/kb/HT1386