How do you remove and replace the trigger spring??
I use the plastic handle to a round file that has a hole in it. I slip the hole over the hammer and then twist handle to grip the hammer as I push down on it. It releases pretty easy using this method and installs just as easily by reversing the procedure.
Once you remove the hammer, it is easy to replace the trigger spring.
I use the longer end of an empty butt stock cleaning kit over the hammer to remove/install it pretty much in the same way as above.