Background Required to understand Quantum Monte Carlo techniques?
Do you have a tame physicist (preferably one who is familiar with Quantum Monte Carlo techniques) that you can talk to?  I don't think it's actually all that hard, but if you try to understand it by reading about it, I strongly suspect that you'll find the books all assume you understand some moderately advanced quantum mechanics/quantum field theory (time-ordered integrals, some non-obvious properties of operators) which they don't explain, and if you don't understand these, you'll find their explanations completely incomprehensible.

I also see from Google that there are lots of different variations on the Quantum Monte Carlo method, some of which will be harder than others, and deciding which one to use for a particular problem is very likely a skilled art.