I looked for your re-post in traditional and maintenance but didn't find it. From my perspective (I'll turn 71 next week) +/- 30 years isn't very old. Your mileage may differ. However, we're not dealing with a valuable antique Civil War type unit here. Cleaning depends a lot on how bad the rust and stains are and what steel the knife is made from. Pictures would help as would information about any markings on the blade. You could have a valuable knife, or it could be a cheap Pakistan knock off. If it's a toothpick made by a known knife smith, or a Randall brand, you need to post more information as any attempt to polish or clean the blade may actually reduce the value.
If it's made in Pakistan or China, then fine steel wool, 000 or 0000, and some oil will take off the rust. The stains may not be removable.
Welcome to the Forum, by the way.