It's actually super easy to install.
1) Remove bolt.
2) Remove IVG and spring.
3) Put 1/8th allen key in hammer lug and back out 4 full turns.
4) Slide hammer out the back of the gun.
5) Compare hammer lug heights between old hammer and new hammer. Adjust lug on new hammer to look as close as possible.
6) Slide new hammer into body.
7) Screw down hammer lug 4 full turns.
8) Replace main spring and screw in IVG.
9) Replace bolt.
10) Pull back bolt and check the gun cocks. Pull trigger and check the gun drops the hammer just before the pnuematics start to push the bolt system back. Or with a pump gun check the hammer drops just as the bolt closes or is about to close off the breeach as you hold the trigger and push the pump forwards.
11) Shoot people. In the face. Lots. Giggle inside. (Only inside, we wouldn't want people to think you are crazy or anything....)