Hi Quizpro, The Troy Shadow X2 is built by Tesoro,(X5&3 by Fisher) and is covered under Tesoro's lifetime Warranty, same as any Tesoro. You say you have had it for a long time so you know most of it's history. Even if you bought it early on from someone else, Tesoro still repairs their detectors regardless of how many owners, and most always at no charge.This is a well known fact known by all long time Tesoro owners(and Troy X2 owners) Corroded Knobs does not sound good and gives way to some question of the detector being submerged in salt water, or some other mishap. Call Tesoro and tell them your story, and whether or not the problem was caused by neglect or by a simple accident, Tesoro will most likely have a truthful and simple solution,(and most likely free) that will certainly be much better than what your "Dealer" has suggested.His "Deal" for you flat out sucks, as he should be telling you the same thing I am telling you.Call Tesoro and speak to Rusty Henry if you can get him and get an honest assesment of the problem, and take it from there.Tesoro has haways treated their folks right, and it pays off for everyone. HH, Charlie