I have had the AMP fork on the King Of Diamonds since 1994. It is still the best cross country fork (my opinion) and most certainly still the lightest out there. If you are an owner of this fine piece of machinery and have not overhauled your shock in the last 6 months, then it is time to do so!
Tools that are need are:
1 pin spanner; Clamping tool for holding shock while unscrewing body; Paper Towel; Shock Oil.
This job can be done in less than 15 minutes when you get good at it. For those that have never attempted this, use safety glasses. You will want to look down into the oil chamber when pulling the shaft and oil WILL SHOOT OUT!
Using
a pin spanner, release the c-clip. Be sure to hold onto the clip when removing
because it will want to fly where light does not shine!
Remove
shock from fork.
This
is a tool made by AMP Research. You can manufacture one or just have PVC
on your vice jaws.
Clamp
firmly enough to prevent the body from turning when twisting the body apart.
I use a thin piece of brass shim material to 'bite' the aluminum. I recommend
using an adjustable wrench or a screwdriver to do the twisting.
The
two body parts
Purging
the chamber with thin shock fluid. Keep poring in the fluid until the shock
fluid becomes clear. 
When
you are use to doing this there will be little need to completely dissemble
the shock, making this a lessor chore. Notice how dark the fluid is. I overhaul
approximately every 20 hours of riding.
IF
you are the type that needs to get your fingers into everything and make
sure any form of impurities are removed, then take the top mount off. 
Now
your fork shock is completely disassembled to the shaft. I do not recommend
to remove the oil orifice.
Boy,
there sure is a lot of parts here! (Just Kidding!)
Notice
the small hole for oil to travel on this side.
On
the other side is a larger hole. I have heard of some drilling this out
for fine tuning, however..
I
use two shock oil weights to tune my shock. 20 weight and 2.5.
Fill
to the threads and SLOWLY move the shaft back and forth until ALL the air
is gone out of the oil. If you do not do this then your fork will have that
HISSING sound when it is working for you. BE VERY CARFULL NOT TO LOOK INTO
THE CHAMBER WITHOUT EYE GLASSES! Oil will want to SHOOT out of the chamber
if you pull the spindle too hard!
Reassembly.
You will know when you have JUST enough fluid when you screw the body together
and the rubber o-ring wants to pop out. I use a Q-Tip for removing small
amounts of fluid at a time.