While Shechting the Korban Pesach is Docheh Shabbos, preparing the Korban by cutting off a Yabeles is not.
So too, while giving a Bris Mila on the 8th day is Docheh Shabbos, preparing for it by checking the baby’s bilirubin is not.
According to the Mechaber, since it is Assur M`D`Oraysoh, one couldn’t even ask a Goy. However according to the Rem’a, one may ask a goy. Ask your Orthodox Rabbi who you should follow.