Generally the iPod 3G is very straight forward, unfortuantly many people myself included have been having problems with the 4G model. When I have time I will write a full how-to, until then here's some hints to help.
If you system isn't picking up the 4G iPod, your not a linux guru and you don't fancy recompiling your kernel, try using Knoppix. You can download this iso (just google for it). This will run a complete linux system from the cd. It also picks up the iPod (any generation) without hassels.
1) If you run knoppix from cd; sda1 and sda2 should automatically be mounted when you plugin the ipod. sda2 is the partition which you should create a dos-divice for. (note that you will have to install itunes on your system before booting the knoppix cd. Once knoppix is booted and the ipod is detected mount the drive where your installed itunes/crossover office and run it.
2) It's worth noting that you can use knoppix to install debian onto your computer with the added bonus that knoppix configures most of your hardware for you (see the knoppix website to find out how). If you do this, your ipod may not be automatically mounted. As root just type the following at the console
mkdir /mnt/ipod (or replace ipod with whatever you want)
mount /dev/sda2 /mnt/ipod.
Now create a dos-device for /mnt/ipod.
As far as unpluging the ipod goes...
I've found on one system nothing worked, however I currently use debian (installed using knoppix) And typing eject /mnt/ipod will effectively eject the ipod. The Do not disconnect warning will dissapear and all is well....
If you need any help just drop me a mail @ dave@windozexp.com