Your music should be in your iTunes library already. If it's not, you can use iExplorer to rip all of the music off of your iPhone and put them into your iTunes and sync them again. Contacts, you can use iCloud, iExplorer or Google or whatever cloud service you'd like really that's compatible with storing contacts. Some users like everything iTunes, me personally, I steer clear of iTunes since I don't exactly like the sync functions. To restore them back onto your 4S, literally just drag and drop EVERYTHING over your iPhone on the sidebar of iTunes.