I have a 05 Boxster S and don't know the answer to this most basic question. Is the shift **** just pressed on and held by friction or is there some technique to releasing it so it slides off the shifter. I tried yanking it up but afraid to get too physical with it.

 

It's basically held on by friction. So, it pulls straight up-and-off. However, be careful -- it requires quite a bit of force to pull it off, and several people have broken windshields and/or injured themselves when it came loose.

Also, you should disconnect the boot from the **** before trying to remove the ****. There's a ring inside the very top of the boot that connects the boot to the ****. Twist the ring 90 degrees (CCW, IIRC) and the ring & boot should push down.