This is a very long thread, but that has already been addressed: I'll repeat the tl;dr part for you: pulsating/vibrating in the steering wheel is a front brakes issue; pulsating/vibrating through your driver's
seat is a rear brakes issue. If you're wanting to just replace to avoid any future trouble, do all four; otherwise, save some money and just do the front brakes (I think have read ONE experience on here of rear brakes causing the trouble, with the front brakes still being fine).
Also, save some money by not messing with it if it ain't broke. I've been reading about this for literally the life of my car and have not changed out anything yet.