another cnc mill questionaire

thank you for your kind answers. for the limiting switches i will use something like these: http://www.google.at/imgres?imgurl=http://www.fischertechnik-fans.de/Images/Tasterinnen.jpg&imgrefurl=http://www.fischertechnik-fans.de/html/Tipps/alternativeteile.php&usg=__cn9bRSjqhrJVgUHl2R2FSplJQJU=&h=589&w=784&sz=73&hl=de&start=0&zoom=1&tbnid=B9XA--RLwVLjNM:&tbnh=113&tbnw=151&prev=/images%3Fq%3Dfischertechnik%2Btaster%26um%3D1%26hl%3Dde%26rlz%3D1C1AVSW_enAT376AT376%26biw%3D1024%26bih%3D513%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=414&vpy=80&dur=432&hovh=195&hovw=259&tx=87&ty=73&ei=kKIlTa3AAYSeOsvd0e0I&oei=kKIlTa3AAYSeOsvd0e0I&esq=1&page=1&ndsp=16&ved=1t:429,r:2,s:0

as a noob i have to ask again: i would think that i need to go with some voltage to the switch wich then goes to a pin on the arduino in case the switch is pressed. am i right? if so, does it matter if i use 3.3V or 5V from the arduino?

another question regarding these switches is, that i thought, that these are also used to set the axis to 0. i mean before the actual cutting starts, the motors should drive the axis to for example axis-min-switch and resets the measurement of the axis to 0 to know where it is, as the stepper motors only measure relativly.