So I'll start off by saying that this is the conspiracy theorists in me talking...and that I should just go to another mechanic and start over.

Background: my 2003 X5 3.0i has very low compression in cylinder 2 and throws the error codes P1345 and P0300. I know those codes are misfires.

The mechanic tells me that the exhaust valve in cylinder 2 in burnt and that I need to have it replaced ($2500 valve job) but that he doesn't have time to do the job then. So a month later when I'm going on vacation we agree that I'll drop the car off so he has a week+ to fit it in. During the week I'm on vacation I call him twice (voicemail) and he does not return my call. Then when I return 10 days later I call again and still no return call. Then I email him and he replies back about an hour later.

He says that when taking off the cylinder head he torques the bolts down in order to test if they will hold when the valve job is complete. In my case one of the cylinder bolts strips the threads. He wants another day to have a guy try a timecert to fix the threads. I say ok. The next day when I call he says that the timesert failed to hold and that he has another method which will add $700 but may not work (in which case a used engine would be neede). I ask how much we are into the repair in case I'd like to minimize my losses. He says 1.5 hours of labor.
So my question is: how is it possible for someone to access the cylinder head that quickly and take the bolts off as well as test the threads for torque spec? Isn't there a lot more involved in getting to the cylinder head than could be done (and re-assembled) in1.5 hours?
Now he wants to buy my car.
Very nice guy (except for when he didn't return my calls for a week), but something doesn't smell right.