Pull the forked end of the shaft through the shimmy damper housing until the hole is open on the opposite end. 
Pour a small amount of 5606 hydraulic fluid in the hole (2 ounces.) 
Push the shaft back through the housing until it stops. 
Remove the snap ring on the end of the housing.

Now, hold the housing with the fork end down and the shaft up.
Do this over a trash can, it's messy. 
Hit the shaft with a plastic or brass hammer several times. 
Keep the forked end of the shaft pushed all the way into the housing when doing this or you will damage the inner snap ring.
You are using the fluid inside to push the end cap (cap is under the snap) out of the housing. 
This may take several hits, be careful not to damage the shaft end.

Once the end cap is out, remove the inner snap ring.
Slide the shaft and piston out of the housing. 
Remove the o-ring in the end of the housing and replace with new o-ring. 
Lay the shaft and piston on a table and with a roll pin punch, remove the piston by removing the roll pin. 
Slide the piston off the shaft.
Now slide the end cap off the shaft and remove the o-ring in the end cap. 
Install new o-ring in the end cap and a new o-ring on the outside of the end cap. 
Slide the end cap back on the shaft. 
Slide the piston back on the shaft. 
Install the roll pin.
Reinstall the shaft in the housing, reinstall inner snap ring. 
Push end cap into the housing and install external snap ring. 

Now pull fork end of shaft all the way out of the housing and fill through the open hole on the opposite end. 
Be sure to exercise the shaft through the full range of movement several times to remove all air trapped inside. 
Keep filling with fluid until the housing is full and no air is felt when exercising the shaft through the range of travel. 

Please check the scissor links for any movement. 
If any movement is felt, shim the scissor links or the shimmy damper will not last long.