I would like to know the specifics of WHY they think it needs a tranny. ML transfer case shift motor failures could cause the same problem, bad control module, can failure, valve body electrics, air mass sensor, I could go on. If there is no metal in the pan, and doesn't make horrible noises, chances are it can be fixed. Get the manager involved. You may just have a noob working on it. Not his fault, he doesn't know any better yet.