I am currently a level 40 human warrior and 97 % of my talent points are in fury because my friend said that fury is the best.

I'm noticing that in p.v.p I die allot and that I'm not very efficient when soloing and
when my guild master ran me through a dungeon as a warrior with prot I started to question if I had made a mistake.

Most of the specials that I use are from the prot tree and I really enjoyed using a shield because I was able to take on more enemies and live to tell the tale.

I heard that its possible to change where my talent points go but that its risky if its done more then once. My friend had to do it to arrange all my talent points in fury.

Is it safe for me to change my tree? Where can I change it and how much would it cost?

This is my first and only warrior so I have no prior experience with warriors and I heard that prot warriors do very little damage, am i making a mist by trying to change my tree?

Finally is it possible to alternate between trees?