You are looking for a 5x115mm bolt circle, a 40mm (or very close to that like 35mm to 45mm) offset, and at least a 70.5mm hub diameter. You need to be at least 16" in diameter as 15"ers will not fit the calipers. Many GM factory wheels will fit your car. All GM big FWD sedans used the same hub, so all the wheels will fit. My '02 Seville SLS has '06 Buick Lucerne wheels on it. But Buick LeSabre, Park Avenue, Lucerne, Pomtiac Bonneville, almost all Cadillac cars from '92 forward, etc wheels will fit. Go to www.gmpartsdirect.com and look for the hub for your car. Then look at the cross reference list for that part. The list is a mile long. Just in case you like the look of a certain factory wheel.
Don
Don