First of all there is no reason to replace a perfectly good water pump just because some of the front is out of the way. I just replaced the original pump on my '88 300E at 250,000 miles.
That said, you do not have to pull the intake manifold, but you will need a universal joint with tape on it to keep it stiff to reach some of the bolts. Secondly there is absolutely no need to replace the pipe that goes across the front of the engine. You will, however, want to replace the soft hoses, especially the one that is about 1-1/2" in diameter between the pump and the head.