Installing new gear shift knob

My car is a 1995/12 mazda 323 sedan, it is automatic, the shift button is at the side (no overdrive), I have been searching on the web for some nice shift knob, most of the have the button on the top, and even some doesn't have button, however some dealer says it actually fits for both top button and side button, is it true?

Will it be difficult to install?

Thanks!