Sounds like you have been at the whipping post for a while. But your background should qualify you beyond the basics.
So, try this:
1) Start Logic, create a new, empty project, and from the main pull-down, click Window, then click Environment (Env).
2) In the upper left corner of the Env window, click on the "down triangle" to have a look at the submenu. You should see, "All objects". "Global Objects", "Click & Ports" and "mixer"..maybe others.
3) Click "Create Layer" then click "(unnamed)" and rename it "MIDI inst 2"
4) Move a little to the right (on your screen), and click the down triangle next to "New" -- Then click on "Multi-Instrument"
5) Double-click on the new icon for "Multi-instrument" and you should get a large pop-up showing the default names for a General MIDI enabled keyboard or soundcard.
6) Under "Device name" -- highlight the default "Multi-instrument" and rename it "Korg"
7) Close the pop-up. Your multi-instrument should now say "Korg" -- both under the icon and in the parameter box to the left within the environment layer you just created.
8) Click on each of the 16 channels in the "Korg" icon so you remove the slashes. This will allow your Korg to be active on any of the 16 channels within whichever MIDI port you select.
9) In the parameter box to the left, click next to "Port" -- you should see your MIDI interface and however many ports are available. Pick the port to which both your IN and OUT MIDI cables from your Korg are attached.
10) Close the environment window and open the arrange window. Under the "Track" pull-down, select "New" and under the "New Tracks" pop-up, select "External MIDI" -- then click "Create"
11) I have been doing these steps in Logic 9, and it created a Korg track, probably because there is only one defined external instrument in this project. I have Logic 8 too, but just in case you need to change your new track -- right-click on the new track and select: "Reassign Track" -- another pop-up window will list several of your layers from your environment window, including your new "MIDI Inst 2" -- Drag your mouse over to the right and you will see yet another pop-up named "Korg" -- and even farther to the right, yet another pop-up that lets you select whichever MIDI channel you would like, or you can set it to transmit on "All MIDI channels."
12) If your reason for doing this is because your external MIDI instrument has some sounds you want to play back or record, and assuming it is multi-timbral...you can repeat this (create new track) procedure and select different MIDI channels for each sound. For instance, your Drums might transmit on channel 10, your bass guitar on channel 7, your piano on 1 and your organ on 4, etc.
13) To select the specific sounds you want your Korg to play, you can click on the information triangle for "Korg" to the left of the arrange window. There, you can select not only port and channel, but also the program (i.e., the sound) you want your Korg to play. If your Korg is not General MIDI, you can rename the "sounds" list by going back to the environment, double-clicking on your "Korg" multi-instrument, and then renaming the default programs to match what is actually part of the ROM in your Korg.
14) You can keep adding new multi-instruments (drum machines, Kurzweils, Rolands, etc) if you want to expand your sound palate.
