oil sensor is in the side of the oil pan. It has a plug with wires as well. Extremely hard to miss and extremely easy to fix. 95 and up 3800s are one of the best engines produced. They may have some minor issues but they are easy fixes provided you and/or your technician knows what to do.
Also if you think these motors have too many problems to be listed as one of the best, think of all the other motors that aren't listed as one of the best lol. Those motors must have way more issues.