iPod / iTunes help! (I want to sync to my PC at work without losing current songs).?

I haven't done this in a while so I don't know if it's risky or not, I have a 80GB iPod I haven't updated in a bit. I have about 5,000 songs on it. I sit at work all day listening to music and I picked up on a lot of new CDs and stuff like that.. My question is, Can I update my iPod from my work PC by adding new songs to my current list without the risk of wiping my iPod clean? I don't want to over-write my music, I just want to add on more to it. In the past when you plugged in your iPod is synced over all the music, I don't want to do that.. I just want to add on more to my current list without over-writing. Is it possible now with the new iTunes? lol it has been a long time since I updated my iPod I'd like some more new music yet still keep my existing songs.

I have the LATEST version of iTunes on this machine, I just want to add songs to my existing list on my iPod (I've never synced it at work, scared to, don't want to lose my music)

And I don't trust "3rd party applications" lol only iTunes.

10 pts :D

Thank you!