depends on how the previous owner lowered it. If it has coilovers, all you have to do is raise the perches (takes like a half hour). If they used really low aftermarket springs, or cut their stock springs, then you'll have to replace the springs.

When a car is lowered significantly, the bumpstops should be trimmed so theyre smaller. That way, you wont be hitting them all the time. So check the bumpstops and see if thely look like they've been cut... they shoud be.