Just out of curiosity, why don't you want to mod it?
Just seems a little odd to me. I totally get wanting to play it at least once vanilla to see the product as it was made by Bethesda, but do remember the construction set is a part of the product.
There a plenty of 'light' mods that don't really effect gameplay, such as all the graphics mods. I'd definitely suggest getting some of the 'must-haves' like a new texture set if you just can't do the dated graphics. Just take a look at some comparison screenshots for the better bodies mod, and you'll see the whole
world of difference some of those mods can make.
Sounds like you can handle the gameplay, which is good.
Personally, I strongly prefer the way Morrowind handles skills in comparison to Oblivion.