After perusing our Forum and identifying most of the "quirks" and problem areas, I have either made the necessary repairs or taken preventive action to avoid unhappy surprises (which no doubt are out there in number just waiting...). I purchased replacement cam shaft and crankcase position sensors to keep as spares/back-up. I also downloaded and printed instructions for their repair. My question is this: Would it be a good idea to just go ahead and replace them now, in the comfort, safety and convenience of my garage? The car has 46k miles on the clock, and I just recently bought the car and cannot determine if the sensors are recently new. Are the replacement sensors bound to fail sooner or later anyway? If I can avoid surprise roadside repairs I would certainly like to. Opinions? Experiences? Advice? Thanks!