Professional Colonic? Not sure yet...

When paying for a colonic (or high colonic) what are the exact mechanics they use? Is the tube inserted all the way to the beginning of the colon? If so, how do they force the tube through the bends and U-shape colon without damaging the colon lining? I have heard of people performing home enemas and puncturing themselves just inside the opening. How would a colonic be safer, especially with someone else doing it? How do they know they reached the end of the colon and aren't going too far in? Honestly, I'm not sure if I trust anyone to do this on me. Lack of experience of the technician, re-used equipment, possibility of damaging colon lining, going too far in...

I know there are possible benefits, but I'm not sure if I want to take the risks.

Am I being unreasonable?