Had new brake pads and rotors installed on front of 94 Lesabre. This was done at a Ford dealer. Was fine for a little while then it began to sqeak when useing brakes. Is it possible This is caused by inproper torqeing of lug nuts? Or use of a different brand of pads?

Doesn't sound too serious. Sounds like they simply used a different grade of pad. Metallic pads squeak after they get seated. They just do. You should compare what you paid with whether or not they put on cheapo "used-car-lot" pads to make sure you got everything you paid for.