Apparently I didn't conduct a thorough search and this has already been done before.

Regardless, this is what I did.
FWIW, I don't like the process of just pulling out the spring clam while it's fully assembled. This could potentially damage the sensor board under the controller, so I decided to do a clean removal.
Tools Used:- Phillips Screw Driver (PH2)
- Small Slotted Screwdriver (1.5)
- Pliers (I used my Letterman Wave)
- Balltop (For comfort)

First, remove the four screw on the top of the unit and set the mounting plate aside.

Gently pull the shaft assembly away from the base and remove the magnet from the bottom.

I attached the balltop at this point to keep the threaded piece of the shaft from annoying my hands. I know, I'm far too delicate.

Now compress the spring by squeezing the plastic "cup" between the spring and the spring clamp to give you some space to work with.

Insert the blade of the 1.5 flathead into the slot on the back of the spring clamp and gently pry it in the opposite direction of the open end.
MAKE SURE YOU HOLD ON TO THE SPRING RETAINING CUP OR YOU WILL SHOOT THE PARTS ACROSS THE ROOM 


Ease the plastic retaining cup off and you can now remove the spring.

Slide the new spring and the plastic retaining cup back on the shaft and compress the spring slightly to put the spring clamp back on.
I like to use my Leatherman to gently ease the clamp back on.

Reattach the magnet and your new shaft assembly is complete! Look at that shiny new spring.


Now you can reassemble your UltraStik 360 and enjoy the much snappier action!