A:
You can go a few ways regarding your music. You can use Google Music Manager, and upload all your music to the Google Play Cloud, and stream all your music, or you can drag the folders of music onto either a memory card, or the on device storage of the phone. There are third party apps like doubletwist to transfer your itunes music onto the phone as well.
In regards to your contacts, depending where your contacts are stored, you can export them, and reimport via gmail, yahoo, hotmail, etc. Gmail, you can import your contacts from a CSV file. in iCloud, i believe you can export to CSV.