Reminds me of the time my CD 6 disk changer stopped working and I asked the local dealer to see if they could fix it. They charged me £50 for looking at it but still didn't fix it. I found out (after scouring the t'internet) that it was just a reset on the unit. I was quite upset that the dealers didn't know this and I wasted £50. I was happy that I still had a working unit though. Lesson learnt. Dealers are and never have been cheap for any type of work, especially diagnostics.
Advice - learn lesson and move on (do the work yourself or go somewhere cheaper).