This shouldn't be a problem - getting it in there is normally really easy.
Firstly get the area ready. Remove the cable and the return spring. Clean out all the crap and old grease. Make sure the dust seal is clean and still grips the actuator drum.
Now, back out the adjusting screw. You'll be adjusting that later. Put a load of grease in the bearing hole and the bearing will just stick in there, even if you tip it upside down.
Line the actuator recess base and walls with grease (don't fill it - or when you push in the actuator the hydraulic pressure will force everything out again). Add some grease to the face of the actuator drum. Fit the components in - thrust ball, actuator race, actuator drum. Check the actuator turns and raises. Now, fit the spring and cable - make sure the cable is not under tension.
And that, my friend, is that. You can find the Workshop manual for the CB350 on line which tells you all you need to know. Good luck. Don't adjust it too tight, remember!