Can I set up my mp3s on iTunes before plugging in my new iPhone?

I'm getting my first iPhone a few days from now, I have a couple hundred mp3s downloaded from mp3skull, but if I download iTunes and transfer the mp3 files to iTunes and set up the album art and names and everything will all that sync with the iPhone once it's plugged in or will plugging it in reset everything making me have to start over again?

I've had an Ipod classic and a touch in the past so overall I know how it works it's just that I've always added the songs after I had the device.

Itunes is a "master" program, if you will. Nothing will be deleted on Itunes because of a device (Iphone, Ipod, etc.) However, the device IS capable of having its data erased if it detects a different Itunes library from your own. I'm sure you already know this.