Difficulty is pretty vague . What are you intending on doing? ..I mean if you are starting from scratch, you would be sculpting casting and pulling the parts ..trimming them..then painting and assembling? With no skill level at all ..ya ..very difficult. If its painting you are asking about ..well, once again ..I have no idea what to go on, to help answer your question ..do you know how to airbrush? If not ..you can pick it up pretty easily ..but I would have to say that most that get it fairly quick have at least a little bit of natural artistic ability ( even if you dont know it yet ..you might)
..Now ..that being said ..there are a ton of tutorials on this forum that help you do almost everything in creating a Predator suit ..read them ..then ask yourself "Is that Too difficult for me?" ..then try it anyways ..you may surprise yourself.
I really cant tell you how difficult it is going to be for you ..only you can answer that question