Shops are male dominated because, for practical hiring purposes, female mechanics don't exist. You'll get maybe one in 30-50 that even apply and that is at a place practicing positive affirmative action in it's recruiting; so even if one of the 30 applicants is female she would need to be better than all 29 male applicants, them's steep odds even if she is better than 80% of them, as you don't compete against the average applicants, you compete against the best.