"...EOS D30 and 30D. (is there a difference?) "
I'm not sure if you were joking here or not, but yes...big difference. The D30 was Canon's first "real" DSLR (not counting earlier colaborations with Kodak) which was a 3 megapixel camera. While cutting edge in it's day, it's rather out of date by today's standards. By comparison, the 30D is one of Canon's current "medium range guns" and like it's predicessor the 20D is an 8.2 megapixel camera. I'm sure there have probably been one or two other improvements over the years as well (although looking at the pictures side by side, they still look pretty similar! LOL!!!).
Okies...like I said, didn't know if you were joking or not, so if not I thought I'd provide some info for ya