Wow, that's brilliant on their part.

First try to remove all the dirt you can from the opening which is contaminated by brushing or spraying with brake cleaner while the turbo is inverted and letting it drain out.

Mix a bucket of paint thinner and degreaser, then immerse the turbo. Blow it out with compressed air. Do this a number of times and the dirt will eventually migrate out of the oil passages and bearings and it will clean up.