How to remove the PCV valve?

Which engine please?

3.0 v 6

That engine has a three piece system, there is the orifice in the valve cover, the tube and the valve in the intake manifold. The orifice is a press in part, you can generally ignore it as long as the holes in it are not plugged. However it can be pried out and replaced if needed. The tubes rarely go bad. The other end locks in and to remove it you need to remove the valve cover connection then rotate the tube and valve while pulling up.

it doesn't say how to replace the plastic elbow without breaking the tabs in the valve cover.

Normally you twist and try to bend it a bit and one side comes loose then rock it the other way to get the other one loose.