Well since circuit city is entirely gone. Do they even warranty their items anymore?
If your light seems dim it may sound like you need a new bulb for your tv. The bubls have an average life of 1000-3000hours of use. In your case, 4 years is long time for the bulb. A replacement will cost you somewhere around $130-$250 depending what kind of tv you have.
Not sure how much it would cost to have someone come out and do it, as they will probably overcharge for parts and 2 hours labor when it takes 15 minutes tops.
this is one website i looked for bulbs www.dlplampsource.com