Done that,
Get yourself a transfer punch set from HF if you dont already have one.
Gently knock out the end on the cap with the clip with the largest punch possible.
Push the black plastic threaded part out the top.
Remove the centerband with another punch (largest that will fit).
Hold these parts in your hand while disasembling and give quick strikes with a small hammer, they will slowly work there way out.
When I put my Jr gents together the centerband is the last fitting to go on. I thread the centerband on the finial and line up the grains, snug the black plastic in the cap and unscrew the centerband making sure it dosent move. Press the centerband into place......