"a friend of mine who lives on the healthy side of the street said that the Master-Cleanse was really hard on the body and that the toxin levels tend to shoot way down then right back up when you are done."
hmm I think that detoxing can be really hard for some, but not necessarily the Master-Cleanse itself as a general rule. If one enters the Master-Cleanse with ails that contradict a fast, sure, the MC could be said to be hard on the body. I would think the toxin levels could actually INcrease, then decrease, then INcrease again according to what we do after the MC, with the first increase being 'things' dying and releasing toxins. The input of toxins being from our diets, prescription/other drugs, etc. I don't believe vegans are immune to toxicity.
"I wanted to curb my sweet tooth and clean out my system." You're getting there! I'm with you... I won't be a vegan anytime soon either (who knows what the future will hold), but I'm certainly on a better track!