I have found the best way of getting a service done, is to specifically tell the mechanic what you want done. When you receive the inevitable phone call saying, this or that needs replacing, simply tell them to do the job they were asked to do, then shop around for quotes to get the other work done (if it needs it at all).
When you get the other work that may need doing you are better prepared for what it will cost you and you'll find it is sometimes a problem that can wait.
My son recently had the bushes replaced in the front suspension in his ute, this ended up costing him close the 3K after the alternator was replaced and a few other bits and pieces were replaced as well. As soon as the gravy train starts, it seems to never stop.
Always, and I stress always, ask for the old parts they are replacing, particularly if it is not a reconditioned part. Quite often your broken/worn part is reconditioned then resold (alternators spring to mind). Buying a reconditioned part is often a case of trading in your old part for a lower cost compared to an original part. If you are getting new for old, get the old part. This tends to keep them honest. If they say this or that is cracked, ask to see the cracked or broken part in-situ on your car, not after it's taken off.