I hear AND have experienced dealership "horror stories" in the past. Fortunately, they were few and far in between.
The Park Place dealership here seems to keep a competent staff of technicians, and if I was a successful surgeon or world-class attorney, I would love to dispense with weekend wrenching and just drop off the car, hand over the keys and say..."fix whatever you find wrong with it".
But at $100+/hr labor, even the most simple tasks are wallet eaters!
I am still shopping or a good "indie" and have found a few, but I don't have any references that can tell me if they are good or not. It's okay to save money, but if they screw up the repair, there is no gain.
Dealerships also have the perks like courtesy vehicles and loaner cars. That may be a costly frill for some, but they know that for their clients, time is precious. Sometimes, I have to decide if I would rather use up what little quality family time I have working on one of the vehicles all weekend, or just bite the bullet and have it done conveniently (and correctly) while I'm doing better things with my time.
Other times when money is tight (which is often, lately), I have to meter out what repair tasks to tackle in order of critical-ness (if that's a real word). Especially with the W124, which is older and has numerous little quirky things that need attention.
I believe, as cars get more complicated and repair expenses climb, society will eventually introduce a sort of vehicle-HMO plan to cover the costs of repair. This would be similar to the current extended warranties that you already can purchase, except, you pay monthly, just like you do with medical insurance...