Sevice Vehicle Soon Light

My service vehicle soon light comes on when it is dark enough for the automatic light control to work. When it is dark I have no interior lights or tail lights unless I turn the head light switch on. I have owned this car for 6 years and never turned the switch on, I always let the automatic senor turn the lights on for me. My question is, the auotmatic light control micro-relay might be bad, is this a dealer only item? I've called car dealers and they say no, I've called auto part stores and they say it is, which is right? Also, are they hard to install and are they expensive? The car is a 1998.

They can be difficult to get out. You might need to remove some of the relays around the one you need to pull out to access it. They are held in place by little tabs. I suggest you try using an eyeglass screwdiver or something small of the sort. A lot of times they can match up the relay at the auto parts store.