Yeah if he is telling you upper and lower ball joints, than you may want to find a more Subaru specific shop. Subarus only have lower ball joints, and they can be had for less than $50 for both of them, one for each side. And the sputtering and low power you're experiencing, could just be a simple tune up, spark plugs, plug wires, distributor cap. And there's a chance the fuel pump is getting tired, but not likely. They usually go forever, until they rust, which shouldn't be as much of an issue as it is around these parts with all the road salt during the winter. It really shouldn't take a whole lot to fix it.