True Nautilus is the file manager preferred by the gnome developers, much like explorer is for Windows.
But that doesn't mean that you're obligated to use it. There are all types of filemanagers available (search the net on tucows or
www.rpmfind.net) my personal favourite is mc (midnight commander) because it's very fast and runs in a text console as well (or a terminal within the gnome environment)
First thing you can do to improve performance is the go in to the options menu of nautilus and deselect the use nautilus to draw the desktop option. One warning though, that would delete you desktop icons since those are drawn by nautilus.
To completely delete nautilus, simply uninstall it or kill the proces in the system monitor.
If you're really looking for speed I recommend changing window manager, I'm using fluxbox, but there are other speedy ones around there as well.
Hope I didn't make things more complicated,
Anne
ps: you can find mc on your RH cd's