1) No you should not. It would be a complete disaster!
2) First answer kind of answers the second, doesn't it?
I don't mean to be harsh. But the truth is, remaking a game with really good graphics for a game with shitty graphics is just too much and would not be as satisfying. You'd need a top of the line modeller, skinner, animator, JASS triggerers, terrainer, and so on...
Making Gears of War for Warcraft is like making Oblivion for Warcraft pretty much. Though with the Born2Modificate pack, probably wouldn't be so bad. But my point is, making remakes with bad graphics is not a very logical idea.
~Craka_J