Steering Failed problems of the 2014 Buick Lacrosse

I was on the highway on the interior lane at 75 mph when all the sudden I got a audible and visual alarm indicating steering failure. I then got the same for stabiltrak failure. The steering assist was obviously gone immediately and the car started floating back and forth. I had my wife and 92 year old mother-in -law with me and it was misting heavily so I carefully continued to drive at a reduced speed. I took the car in and they said the steering was not getting electricity. Also, they said the passenger side rear wheel sensor went out which caused the back and forth motion. The car dealership wants to charge me $3400 for the repairs. I see that there were recalls on other gm products for the steering on similar models I. E. Cadillac etc. I found several instances online for Buick Lacrosse but for some reason not all were reported. I bought this certified vehicle may 2018 with 19,520 mi. Which is at around 42,500 mi. Now. I am very concerned about the safety of this product in the future and would like for n. H. T. S. A to take another look at this steering issue and why these two issues with the sensor and the steering occurring at the same time.