Sable with stiff steering?

First you need to check your power steering fluid. You need to eliminate a hydraulic power steering pressure loss. If you power steering is fine you may have ball joints binding or outer tie-rod ends binding. With out knowing exactly what the shop did for as repairs to your car it would be very difficult to see if there is a relationship between the service they performed and the problem you are experiencing. You can always take your vehicle to another repair shop for a second opinion. Something like that should be a free estimate unless they have to remove front end components to determined if the problem is power steering or steering and suspension.