Not bad for a (self confessed) newb.
O.K. repeat after me;
Go get and burn it - you will grow to love this disk. A stand-alone distro worth it's weight in gold.
Haven't checked, but it *will* support SATA - I'd be sure of it. Get 3.9 (or 4.0 maybe if it's out yet).
Be aware that for safety Knoppix mounts all the disk partitions read-only. You have to remount them (just right-click), or maybe go get systemrecuecd (as well) and use that. Both can be got from the LQ download site.
The early loader portion of grub uses (relative) sector counts to locate what it needs. So forget trying to work it out. I don't know RHEL at all, so I couldn't guess where it would install grub - that said, /usr sounds mighty unlikely. /boot/grub would be where I'd start looking.
From a terminal try
locate menu.lst (that's list without the "i")
You'll probably find all the stage files in the same directory. You can do all the moving of the partitions from the CD based distro, and then just re-install grub from "rescue sysimage" (I think that's what RH called it). Simplest is generally best when screwing with your data.