Vehicle driving very stiff/hard ride after lower control arms replaced

Well, after replacing something like that you can expect a firmer ride since the rubber parts used to attach the control arms tend to wear out over time giving you a soft ride. But I would not say that it should feel "extreme".

We made them drive it again. Now they are saying the shocks and struts are shot. We had no driving issues before we took it in. It went in for a check engine light. Why would we not have any driving issues before but now we do after the control arm replacement? And shouldn’t they have know the shocks and struts were shot?

So what sometimes happens is if the struts are close to going out when they are fully extended for a period of time they can "lock". This cannot be avoided when the job is done and there is no way to tell when they are out. Just one of those things, no one is to blame. here is what needs to be done to fix the car. Check out the diagrams (below). Please let us know if you need anything else to get the problem fixed.