Okay, first of all, its called Elder Scrolls IV: Oblivion, not morrowind oblivion.
Thats aside lol, there is no real way to answer. Bethesda hasnt released any official requirements, but in an interview, a Bethesda guy said that the game will leverage the latest hardware, but the devs were also trying real hard to get the game to run on a wide variety of hardware.
Definitly get a gig of RAM, and that should be sufficent for decent graphics. Your video card and processor should be fine as well. Dont expect to play the game on highest settings, as it just wont. Look at the screenies, and you'll get an idea of the power they require. If the game is a hog like BF2 or FEAR, you can get an idea of what the game will require. However, i have more faith in Bethesda than I do in EA. I think you'll be fine.
I think you'll be fine for medium settings, maybe with some settings set on high.
I'm also dying for this game, cant wait for it!