Dick,
It is quite straight-forward, and as you proceed, each next step is fairly obvious. I had to do all this last year when the gear shift cable got a kink in it and "froze", and did it without instruction (and I'm mechanically a bit inept!
).
I'm not at the boat at the moment, but on ours I had to remove the Ritchie compass on top of the pedestal (4 corner screws) and lift the compass off. Then looking into the pedestal there were four more bolts holding that next piece onto the main base. Main caution is not to drop anything down the centre of the pedestal (it will likely come out the bottom but could roll into the bilge area from there).
The cables are held on by cotter pins in a fitting (again pretty self-evident), the throttle/shift levers on ours are held on by allen screws.
While you are in there, you might want to check and oil the chain, but be careful not to get any oil on the brake area (you will see the small pads there if you have a brake, and they need to stay dry or the brake will slip).
I replaced both the throttle and gear shift cable, and found it much easier than I had anticipated. The only tough part is to get the adjustment right, so the transmission shifts completely into both forward and reverse gear, and the throttle moves correctly to get the right idle and full throttle.
That's as much as I can recall, but feel free to ask questions. Others may have a more technical or knowledgeable explanation.
Good luck!
Frank