that guy lied...struts for an sts (like everything else) are expensive. like 1500 bucks for a set of factory ones..plus install. there is a company online that sells an aftermarket set of struts (assuming thats what is wrong) for much less. i think the company is arnott or something like that. do a search online for them. they could save you a few bucks and there products are great...i want to say the struts are like 500 bucks from arnott. but its been awhile. and this is assuming thats what is wrong with your car...cant tell by not seeing it in person...sorry
however it sounds like more than a strut...a strut basically acts like a spring and a shock in one unit, they control keeping the car level and absorbing bumps..they dont control steering...sound like you need more than a strut