I personally would liek to do it myself because I enjoy it but more importantly I know it is done right. Also, in the process I learn a lot. Sometines, it is not the hourly rate but also if the mechanic has proper tools to do the job or else you will have another expensive repair down the road.
I torque doiwn all the nuts and bolts as per spec which generally most of the mechanics do not bother.
Many mechanics would not bother to lift the engine with the hoist but would lift it by the pan which is quite dangerous cracking the pan even with the wooden block because of the weight of the engine. Sometimes the crack is not immediate but has fatigued the aluminum where it develops gradually with time.
Anyhow, there are many good and honest mechanics.
Above all, one has to have the time and patience. I have 5 cars, so I can afford to take my time.