travel between countries

I just put this message on the main Africa In General forum but then saw this Zambia forum. My question is this: Is it easy or difficult to travel by car into, say, Dem Rep of Congo, from Zambia. What paperwork is required? Does it make any difference that one would be traveling just to the next village for an hour or two then return to Zambia? I have always been curious about this subject of traveling by auto between countries in Africa.....thanks Dave Bruce