I'm going to echo what others have already said: Second World Sourcebook is an excellent resource in this area.
I ran a campaign that lasted about two years in a sort of broken pattern universe that was highly successful. The basis of the game was D20 Modern, but I used the Second World Sourcebook to tweak individual settings extensively. I basically wrote up a template and applied it to different locations the group went to, and devised some basic rules for editing the templates by powerful (amber level) characters.
It really wasn't that hard to do, but if I were going to run a full-on Amber game with those rules, I'd use some sort of alternate death mechanic, as Amberites are extremely hard to kill.
--Steve