Does going to a shower have the same spiritual effects of a mikvah? if so, does one need to do anything special? A certain duration of time? Kavanot? Completely covered?
No, a shower does ont have the same spiritual effect as a mikva, and a pool of 40 sa’ah is required, with a number of additional halachos.
A shower is (possibly) suffient for fulfillment of the enactment of splashing 9 kabin of water on somebody who saw a nocturnal emission, but not beyond this (some question this, because the shower head is connected to the ground, and this is not a vessel).