I have a 2006 Aveo with 71,000 miles, took it to the dealer today for an oil change and he told me I need both front and rear shocks, the evidence being that the rear tires are starting to "cup." He rotated them to the front but suggested that l also need to replace those tires. His estimate is $1100 just for the shocks and rotation, not counting the tires. I am wondering if cupped tires is enough evidence to spend all that money. Thanks.