I think I can help with the 3G... Try updating your PRL by calling *228 then press 5 when told to do so...
As for the wifi, if you already connected to the network before, tap on the network, tap forget then tap the network again and enter the password and try to connect again. If that doesn't work, then try and connect using another device and see if it works. If it doesn't work on another device then reset your router to factory settings.