It seems like you have some really big issues going on. Let me see if I can help. First of all, wether you use the Midi cables or the Serial Connection, will not affect the sounds that the Korg N1 produces. Those are only methods to get the Midi instructions in and out of the keyboard from the computer.
Second, if you are using the Freestyle that came with the keyboard, you might be better off using Cakewalk, and getting yourself and instrument file for the N1, the darn thing has 18megs of sounds, too much for one human to be able to go thru and remember. Using the instrument files will help because the program names(sound names) are in the instrument file.
The GM sets. Korg N1 is setup with the following groups(sets of sounds)
Each one has a version of GM sounds, and are designed to map to GM,XG, or the other one(can't remember off hand), and the third set is for drums. Now this is not by any means all the sounds that are available in this board, just the GM ones.