Adding the weight does almost nothing to change the alignment (a good shop though will always align the car with the way it is driven most often). It typically adds -.1* of camber to the front right and that's about it.

In all the alignments I have done I have never had an instance where I have needed to reset a steering angle sensor. The only time I have had to worry about resetting the sensor is if the rack has been disconnected from the linkage.