Lutheran ministers are referred to as Pastor or Reverend not Father. It is established this is a Lutheran church as Bill and Nancy leave the church.
When the woman in the opening scene removes the container of milk from her grocery bag and puts it in the refrigerator, it's a modern plastic milk container, not a late 70s one, which were still cardboard.
In Season 2, when Tench moves into his own office, there is a whiteboard with notes and clippings on the wall. In 1979-81, that would have been a blackboard.
This episode is set in 1980 but there is a Chevrolet Celebrity outside the church at the beginning of the episode. This car was not sold until 1982.
Chevrolet Celebrity is seen parked in front of the church. This car wasn't introduced until 1981 and went on sale in 1982. The story took place in April 1980 as shown on the cheque made by Mr Ford.