Pimp G3 with S-ATA

I don't really need a new apple computer but am quite fond of the G3 400 I still have. This thing is noisy though and the hard disks are the culprits. I am thinking about using an IDE->SATA adapter and changing the two IDE disks by either a 2,5" SATA drive or an SSD. I researched a bit and 128GB max should work.

Additionally it might be an option to turn off the big fan inside the housing so that just the power adaptor fan keeps running. My assumption is that that central fan is there to cope with the heat that comes from the hard disks. Never had the impression that the cpu heats up badly.

What I don't know is how to easily move to another hard disk. On windows machines I use some cloning software but I assume that won't work with drives from macs (not sure though). If I recall correctly with Mac OS you just copied the files and unplugged the old disk but how is that with OS X (10.4.11 to be precise)?

Any comments/Help is much appreciated.