After field stripping the Glock, grasp the front portion of the receiver
and remove the locking block pin with your 3/32" disassembly tool (see
figure 1). Model 17, 17L and 19 do not have a locking block pin, so skip
the above step for these models. Remember the locking block pin is the
first pin to be removed and the first pin to be reinstalled. If you install
the locking block pin after you install the slide stop lever, you will
bend and damage the slide stop lever spring.

Next, remove the trigger pin. To facilitate trigger pin removal, the
slide stop lever should be moved forward and rearward while applying pressure
on the trigger pin (see figure 2). DO NOT use any
excessive force (such as a hammering implement) to remove the trigger pin.
This will unhook the slide stop lever spring from the groove in the trigger
pin. Remember to remove it from left to right!

With the trigger pin removed, withdraw the slide stop lever by pulling
it back and out (see figure 3.). NOTE: When reinstalling the slide stop
lever in the pistol, be sure it locks into the grove in the trigger pin.
To function check the slide release lever, lift it from its rest position
and release it - it should snap back into position crisply. If it fails
to do so, make sure the spring is not binding or bent and check to make
sure the slide stop release is riding in the groove in the trigger pin.

With the locking block pin and trigger pin removed, use your disassembly
tool to raise the locking block (see figure 4). Note: Pry up from the left
side of the locking block to avoid damaging the trigger bar.

Now move to the rear of the gun and use your disassembly tool to push
the trigger housing pin out (see figure 5). Remove the trigger housing
pin.

With the trigger housing pin removed use your disassembly tool to apply
pressure under the ejector to raise the complete trigger assembly from
the receiver (see figure 6). Then raise the rear most portion of the trigger
assembly above the receiver and withdraw the complete assembly (see figure
7).

Next comes the trigger assembly take down. Hold the trigger assembly
as shown in figure 8. Pull forward on the trigger with the trigger bar
while rotating the trigger bar counterclockwise (see figure 9). At this
point, the trigger with trigger bar can be lifted from the trigger mechanism
housing.
Separate the trigger with the trigger bar from the coiled spring by
working the hooked end of the trigger spring off the trigger bar. Separate
the trigger mechanism housing from the trigger spring. Note: Notice that
the opening of the spring faces up in final installation at the point where
it is installed in the trigger mechanism housing - go to the linked diagram
below to see a graphic of the final installation.
Diagram of finished spring installation

Remove the connector, as shown in figure 10.
For reinstallation, just reverse everything and don't force anything
into place.
Trigger kits available