little me

here's an example of the kinds of problems i'm facing at my new job:

the department where i now work has been offering some esl courses to the engineering and geography departments (don't get me started on that!) for about 15 years. no full-time person worked there. one person, we'll call her mary, has been working (part-time) as the supervisor of 5 part-time esl teachers for many many years. mary is excellent at her job and the esl teachers have worked well with her. last year, the department has decided to create a full-time esl position that would kind of take care of all this and help the esl section work better (and ultimately become a separate department (don't get me started on that one either!)). many people applied for the position, including me and mary. i got the job. mary didn't and is still employed only part-time by the university. now, mary works "under" me, between me and the 5 esl teachers who, every year, don't know if they'll have a job or not, depending on the number of esl/bilingual students enrolled that year. i'm going to have to supervise 5 teachers without knowing a thing about them, how they work, why they do things the way they do them (and trust me, i don't know if i'll ever understand why they do certain things the way they do!), and to tell them what to do when mary's been doing this very well for many years. i am not confortable at all with this position, to say the least. what am i supposed to do? tell them that everything they do is wrong (after all, that's what i was hired for, right?) and change the whole darn esl program and they'll all hate me? tell them that everything they do is great so that i don't offend anyone and change nothing? how can i become the leader of a tight group of people (definitely much older than me) whose names i don't even know and that's been working so well for so many years? where can i find the authority and how can i become respected?