The 50mm will not AF with your D40.

If you bought the kit, the 18-55mm EDII is as sharp as the 50mm.

Only that it can't go as fast as F1.8.

Trust me.
Without the 'split focusing screen', one can't do a perfect manual focus.

Back in the manual days, there're the 'split focus' 'matte focus' & other various types of focusing screens.

I quote from a forum:
"A split-screen focusing aid is that little circle in the middle of the focusing screen that looks like it's been cut into two equal parts with the cut usually running either diagonally at 45 degrees or horizontally. Each half of the circle is actually a small prism.

The way that it works is that when you point the circle over a subject that has vertical lines, when the subject is not in focus, the top half of the lines will not lineup with the bottom half. When you adjust the focusing ring so that the subject is in focus, the lines will all line up perfectly. The diagonal split has the advantage that you can also focus with it using horizontal lines."

Something like this: