Hello,
Did it several time on various Supers: No special skill level is needed but it is painful, specially because you must sometime work upside down.
Easiest way is to remove 1st the speedo (same arrangement as the clock, with 2 small nuts on the back+ Speedo cable, then you have a good access to te clock.
To do so you should remove some hardware from the under of the dash, 1 bracket and 1 air duct, as far as I remember.
Be careful when removing the speedo, because the paint of the instrument cluster can be chipped very easily, and I'm afraid that you'll have to disconnect everithing: Speedo cable, of course, but eelctrical connections also. Some pics with a digital camera will be of great help for refitting.
EVERYTHING SHOULD BE PERFORMED WITH BATTERY DISCONNECTED, of course.
regards
Sébastien