Syncing device with TON of music, what'll happen?

So I have an IPod touch with a lot of my music and all I want to do is put it (music) on my computer so I can than download it to my new iPhone but I read somewhere that if you sync a device with music the music is erased and that Can't HAPPEN! Please tell me what would happen and how I can prevent delete-ery

If you purchased all of the songs through itunes store, please follow these steps:
1. Open up Itunes and Click on Itunes Store
2. Once you're in the Itunes Store look to right side of the screen and you should see the word "purchased". Click purchased and you'll be sent to a purchase screen.
3. Click on "All Songs" and then it will show all the songs you've downloaded. From there you just hit the button that looks like a cloud with an arrow on it, and it will download all the songs all over again.

If you didn't purchase them through Itunes, then you'll have to download software that will strip the songs from your iPod onto your computer. And here is a step by step guide show you how to do that.
http://www.ipod-transfer-copy.com/how-to-transfer-music-from-ipod-to-computer-itunes.html
Hope it helps. Feel free to email me if you need further help.