Can anyone help with shifter bushing replacement?

Trying to replace the shifter bushings- I have the white O-ring thing and the cap that goes on the end of the shifter (I think/ hope they fit).

I can't get the shift lever cap to budge. I know I'm supposed to press down and turn counter clockwise, but I can't get it to move more than 1mm. I can't get it to go down any further and it doesn't turn in any direction.

I wanted to see if anyone nearby has replaced these, and if I could meet up for some help.

 

I've done them, use some big needle nose pliers to push down on the collar. You sometimes have to put a bit of grunt into it.