Do you have to disconnect the cables to lube them ? How often should you lube them ? Whats the easiest and best way ?

Yes you do have to disconnect the cables up at the handlebars to do so.

In order to remove the throttle cable you will have to take the 2 screws holding the electronics apart as well.

I found when trying to put the clutch cable back on the handle that I could use a 3/4" open end wrench to manually engage the clutch at the transmission, therefore giving me more cable to work with getting it back onto the handle.

And when you put it back together be sure you leave the appropriate free play in each cable (have to look in the manual again for the exact amount) or the clutch will not fully disengage.