Munnstang,
Well that depends on how the internal cable looks. You have to remove the gauge cluster to get to the speedo cable. The cable releases from the guage by squeezing the white part, don't use force it should just slip off with the white part squeezed.
Use disposable rubber gloves and pull the inner part of the cable out all the way slowly coiling (about 8" dia.) it as you go. Clean the cable and check it carefully for excess wear or fraying. On mine the original lube had turned to a guey mess that was very hard.
I replaced the inner cable with a new one, take the old inner to a speedo shop and they'll make you a new one for $15. They'll also give you some special lube. Install the new cable with gloves and lots and lots of grease as you feed it in.
Good Luck, Don