Contacts would depends on where they were saved, if you saved them in your GMail account or some other central place like your provider cloud storage then yes they will come through. If they are on the internal phone or on the SIM and you are not using the same SIM, you will not get contacts back.
The apps, I have seen them install automatically and have seen where you need to install them manually. It's not too big of a deal to just re-install them.