I've had both ends of the stock cables loose at one time or another (not both at the same time, maybe that's why it was a real pain getting the little barrel ends back in place at the throttle grip end). I can't see that it would be that difficult but it would depend (as usual) how mechanically inclined the individual is.
I believe, given the challenge, the cables could be changed in about an hour or a little more. Raise & prop the tank, remove the overflow reservoir and gain access to the lower end. Then with those loose (and marked with a marker or tape to know the setting points), the upper end at the throttle should be a breeze.
Just don't take my word for it though. I've been know to make all jobs I do take longer, except for the ones involving sex.
See ya.