as long as they are from the same generation. the newer ones have different ide pinouts then the older ones
you'll probably have to swap the drive, then flash the firmware from the 160gb version to the 30gb ipod
be careful popping that ipod open, the halves are held together using glue AND plastic clips. the glue is the easy part, keeping the plastic clips intact is the hard part. be sure to use a tiny flathead to push them in as you pop them apart. dont fret on the glue, it still sticks back together pretty well when you piece it back