Start here: the biggest risk is operating on the wrong problem
Asymmetry has many causes, from a short jaw on one side present since birth, to condylar hyperplasia in which one jaw joint continues growing into adulthood, to old trauma, to facial nerve weakness that shows only in movement. Each needs a genuinely different treatment, and several need investigation before any operation is even considered, because a progressive asymmetry corrected surgically without addressing why it is happening will simply recur.
For this reason, any plan that begins with a specific procedure rather than with photographs, a clinical examination and usually a CT scan should be treated with real caution. The assessment is the part of this process that most determines whether your money is well spent, considerably more than the surgical technique itself.