Getting a new 3Gs and have a few questions

I am getting a new 3gs because of dust that started appearing under my screen. Anyway I am new to Apple since my iPhone and I do not know how the restore process works very well. My iPhone backs up every time i sinc but I'm not sure if it does anything with my contacts. I have all of my music and apps set to sinc automatically but my contacts aren't set to sinc and they aren't on my computer. Will I lose all of my contacts when I restore or any other information?

 

Well I am getting an advanced replacement since I am not close to an Apple Store so they are sending me a brand new phone.