For the gearknob, i would just get a new one. Otherwise, u could remove, sandblast it and then apply plastic primer, paint it (then clear coat).
I am doubtful if the new paint job would last in such a highly used item.

For the cruise control plastic surround, you will need to remove the part so you can do the same as suggested for the gearknob. You will need to remove the whole steering wheel first. I wouldnt recommend sanding it and painting it while its still on your steering wheel... I imagine the replacement part would be quite pricey if the CU2 woodgrain unit is anything to go by...

Out of curiousity, do you (or other drivers) wear rings? Or is the car out in the sun regularly?