I am Mike Moore and Ilive in Northern California . We bought a 2017 LaCrosse Premium in Dec 2016. It now has 34,000 miles on it. I had the oil changed this morning and got a call from the owner (friend of many years) wo said I had a leaky rr shock, and they were electronic (damp rate adjustment) and he thought they were $500 each and I ought to see if they are under warranty.
I did find the p/n GM845550899 and can buy them for $180 (GM part) from Rock auto.
Do they have to be replaced in pairs?

How tough are they to replace?
Thank You
Mike Moore

 

As a general rule, suspension units like shocks and struts are best replaced in pairs, assuming the existing ones are of approximately the same age/mileage. It might be reasonable to assume that if one side has failed, the other may not be far behind.