Does syncing my iPhone 4s save my contacts, photos, messages, apps, etc?

So my phone doesn't work anymore and i will get it replaced with a new one at sprint. Once i get a new one, if i sync it with my laptop, get i get my old data back? Even if its a different phone?

Yes. Make a complete backup of your phone by syncing to iTunes. When you get the new phone you restore from iTunes backup and it will pump over. Best luck.