All the nikon cameras can produce good photos. Its working within the limitation of the camera you have. Understand how they work, and you will still get good photos. They are not miracle products designed to shoot perfect shots by themselves.if d40 got a problem, d50 is worse... d50 viewfinder is even smaller than d40.
Back with film SLR, the usual range is 28 - 80mm. The 18-55mm kit lens for Nikon DSLR is extremely light. There is always the physical zooming too. Usually, 18-55 is the general range, unless its physically not possible to change your position or the position of your subject.
Its not the VF that affects your ability to MF. Its rather in the older film SLR, there is the focussing screen that you look through the VF that aid in MF. Nowadays with such good AF, I hardly ever use MF anyway.