2002 Subaru WRX with 125k. The check engine light recently came on

I have a 2002 Subaru WRX with 125k. The check engine light recently came on and my mechanic is saying that one of the four cylinders is failing. Note that this mechanic performed at 60k tune-up. He is suggesting that at a minimum I replace the failed head and that I should probably do both considering the small increase in labor at that point. I'm willing to have the work done, but am concerned that the perhaps this isn't the actual problem?

Answer:

I would not commit to a head(S) as 125k and being a Subaru. Rarely are the heads a problem. I would get the trouble code and CLEAR explanation as to why they want to replace head. There could be so many other min- minor things affecting the cyl. I would def get a second opinion. I am not ruling out a possible headgasket etc.. but.. this is a big job, lots of $ and does warrant a clear/ accurate explanation as to why they are quoting this work