I changed the strut/springs out myself. I believe the parts were ~$650. I have air tools and a spring compressor. There were a few tricky reaches that required a helper and you need to remove the back seat. If you don’t do it yourself I’d buy the parts and find a good shop to do it for you. For me along with getting rid of the terrible Bridgestone oem tires, it greatly improved the ride enough that I no longer wanted to get rid of it. To me, Toyota made a huge mistake with the original rock hard ride and word got out and it dampened enthusiasm for the Avalon. It could have been a much more popular car.