Bao:
As J. Chambers noted, the "condensor" (actually a capacitor) mounted on your generator is there to lessen radio interference caused by generators and ignition systems. These were quite common years ago on virtually all cars, but most newer radios and alternators have built-in capabilities to deal with interference. They were typically mounted in the ground circuit of the generator. Here's some examples of early VW applications:
As for the fan cover plate, the slit is there to divert a small amount of cooling air to the generator. I've always heard that the vent should be positioned at the bottom. It's a good idea to have a brush cover installed to keep dirt (and accidentally dropped parts) away from the internals. Finally, double-check your generator numbers to make sure you have the proper replacement for your fan mounting setup and your voltage regulator.