I just removed one that was extrememly TIGHT!! Be sure the hammer is cocked and the safety is on.
Remove the assy pin.
The trigger assy must move forward as part of it's removal, but it will not because the safety button will hit the receiver....
If you can reach in under the front of the carrier, pull the front out of the receiver. It'll only go so far, but far enough for the safety button to clear the receiver. The assy may be really, really tight, so a light tap with a plastic hammer or screwdriver handle on each side near the front of the trigger guard may help.
Once the assy is raised in the front, press the bolt release and push the carrier to the center of the magazine follower. You may need to depress the bolt release button....push it all the way in.
With the carrier at the center of the follower, you'll likely need to tap the trigger assy forward. As it moves forward, the end of the carrier will lightly depress the mag follower.
Keep moving the assy forward until you see the end of the mainspring tube. At this point the housing can be lifted out....probably by tapping once again with a piece of plastic.
Dissassembling the trigger housing isn't all that difficult, so if you want to take the housing and lay it on it's side on a piece of sandpaper, sand the sides a little to give it some room during reassembly to the gun, otherwise, you'll be fighting just as much getting it back in and aligned properly.
Doug Braker