Ck Engine Light Bulb

A mechanic sez my car won't connect to the computer because the "check-engine" bulb is burned out. He wants $104.00 to fix it because he has to take out the dash.

I took it in because it is idling really rough like it wants to stall all the time.

Is this a reasonable repair price? It seems high to me.
I was told the oxygen sensor needs to be replaced. When I bought the car a few weeks ago the previous owner told me that was repaced. Are there TWO oxygen sensors!

Can anyone help! Thanks!