For starting off, I'd not get too hung up over ultimate sharpness. As the other folks have said, there are many lenses which will give you excellent results without spending mega-money. Not to mention that compared to 35mm (is that even possible?) 4x5 is hugely forgiving.
However, you are probably better off sticking with shuttered lenses, at least until you get used to all the mechanics of working with the camera.
Finally, welcome to the large format world!