Mullerectomy: is it very much complicated/complex/uncommon?

I'm 22 and I'm supposed to have a mullerectomy due to an acquired Horner's syndrom. I talked to some doctors, ophtalmologists and neurologists, and not all of them know about this kind of surgery. I wonder if mulerectomy is a very uncommon/complex surgery... If you would classificate the difficulty the surgeon has when performing a mullerectomy, from 1 (very easy) to 10 (very difficult), which grade would it be? In other words, how mullerectomy is seen from the surgeon's point of view?