My $0.02 - pay the $20 + shipping. Have the oil analysis done. Run your rig at -least- 30 seconds (pref 1min+) at idle before shut down. This, as others have stated will allow that hot turbo to cool a bit. BTW - an aftermarket stereo helps with this - cool down and tune in, etc...

You'll feel better, I imagine when the oil analysis comes in. Sooty oil (or quickly very black oil) can mean a few things. 1. you have a diesel engine (you don't). 2. you have badly worn rings and you're blowing combustion products (including smoked oil) into the pan. 3. you have cheap oil or 4. you have a turbocharger. There can be other reasons like VERY bad fuel and poor oil circulation to name a few, but... I think you're OK.

Pull the dipstick - rub the oil between your fingers. If the oil feels nice and slick for a good 20+ rubs between your thumb and forefinger you're probably ok. If it starts getting 'sticky' or feeling like it's not lubricating any more? Then you might have a problem. This sure is subjective and nowhere near 100%, however it'll tell you if you're breaking down your oil - because if you are it'll stick quickly.