A firewire enclosure kit with a drive you buy is fine.....and firewire is the way to go....but you may wish to consider getting a combo usb2/firewire enclosure just for portability.
100gig is not needed for ripping and burning, you should however have at min 5-10 gig free for the process, and then whatever amount you need if you choose to keep those rips on your hard drive (4 to 9gig per movie uncompressed) to watch on pc...ie, whatever your wallet can handle..
I personally like Seagate and IBM/Hitatchi, but any "brand name drive will do" just make sure it's udma100+ at 7200rpm. Alot of high capicity name brand drives that are sold "cheap" are at 5400rpm, you do not want them.
As for ready made external units.......I can tell you personally, I've had bad luck with Buslink products, but these were USB2 only devices.
Good Luck and let us know how you make out on your project..