for sys requirements visit autodesk's website..
and for rendering an entire scene, it depends on the complexities of the scene.if u have a simple scene then u cud render all of it in a simgle pass.but if u have alot of objects in ur scene,i wud suggest to render in passes.render different set of objects in different passes and then later composite them together..thats a better wat to handle objects without wasting too much time on rendering everything......