This has got to be an easy fix as it seems to be only a corrupt map. I don't understand what do you mean by you're 'stuck on step 6, my garmin wont connect to pc' This is step 6 & 7:
6. Then press "Updater.exe" button, which will launch updater.exe ready for flashing the firmware. Also you can drag the firmware files from the rectangle displaying their names.
7. Then put your device into pre-boot mode and flash the firmware with updater.exe. Search through this forum for what is pre-boot mode and how to flash devices with updater.exe.
Maybe you're not getting into preboot correctly. Do this:

1. Make the cure firmware as per step 4 in the cure 3 thread.

2. Follow step 6 as above. Select the radio button next to 'USB device' in updater.exe and have it visible.

3. To put your 50 into preboot mode this way: Plug a usb lead into a rear port of your PC. Hold the top LH corner of the screen firmly with your left thumb, left fingers behind the unit.

4. With the unit fully OFF, plug the miniUSB lead into the nuvi and watch updater.exe for your nuvi's details to appear in the window adjacient to 'USB device' which indicates it is in preboot then immediately click 'OK' or hit enter on your keyboard. Keep holding the screen firmly until 'Loader'/'Software Loading' appears on the screen.

5. When it's finished, it should enter Mass Storage Mode and be detected by Windows.

6. Delete the Korean map.

7. Flash the full original firmware.

Next time you get some dodgy map file, put it on a microSD rather than on the unit. That way if there's a problem take the card out and the unit will boot normally.