I have an '03, 3500-SWR, QC, HO, stock steel wheels and tires, with 28,000 miles. I just noticed a very slight "smudge" of what might be oil on the left-front stock shock. The truck seems to ride O. K. Just wondering if it's time to consider new shocks? I've been hearing about the Bilstein"s and the Rancho 9000's. I would,very much, appreciate Your opinions and suggestions. Also, where's the best place to buy them? Thanks, in advance, for Your help. Joe F.