Actually the best thing to do is send the camera to Eric Hendrickson for a CLA (clean, lube, adjust). I just got my S1a back from him, will be sending him my Spotmatic next month and probably my H3v or one of my MXs the month after that. Here's his website.
Home Many of us on the forum here use Eric and consider him the best. After you ship the camera to him, he sends you an estimate and will ship it back to you if you decline but his prices are probably the most reasonable you will find.
CW