As always, Steve gave a very insightful response. Now that I have done this, I can see that the tech needs to know the trick and use the right gasket sealer.
In the real world, it doesn't work this way, but if I could line up as many of these jobs as I could do, and get $200 a shot, I would make alot of money. In the real world, it doesn't work that way for the profitability of the shop. I can see where Steve's guys could do these in 1.5 pretty easy. They've done it before and know how to be successful. If you take it to someone who has not done several of them, they will have to spend that several hours to get it done, and their chance of success is greatly lowered. I'll bet Steve could make a very safe bet every time his guys do one, that it will not leak. If he put a new guy, even a good tech on the job, he couldn't make that bet the first time or two the guy did it, although it would probably not leak.
Then there is also other wisdom in his response that you should listen to. He explained that doing this job thoroughly involves checking other components and possibly finding tensioner problems etc. If this occurs, fix it all. If these engines are right, they will give you many good, trouble free miles.
If the leak is very small, actually I wouldn't worry about it. If it were my car, and I were going to pay to have this done, I would want to have this done by a tech that has done several before successfully like Steve's guys. Even if the job pays 3 hours, and the guy does it in fifteen minutes, it should be of no concern. You are getting your moneys worth.
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in