Engine light and possessed AC circuitry

Hello

I am knew to this and I need some advice. I am sorry if I offend in anyway. Here is what I have.

2006 Tacoma Access Cab SR5, 4 cylinder, automatic.
I have on occasion thought that on start up the engine sounded a little rough but then again it could have been my imagination. About 4 weeks ago the check engine light went on and for a 30 second or a bit more the engine was running really rough. My mechanic said I needed new coils, spark plugs and flush/clean out the injectors. After that and a whole lot of cash the truck seemed to work really good.

About two weeks ago the same engine light with the same symptoms happened again. This time I went the the auto parts store and borrowed their code reader. According to them the code was for multiple cylinder misfires. I then remembered the that each time the AC was on. Until 7-13-1017 I made sure that I started the truck without the AC engaged. On 7-13, I was driving and needed heat from the AC system and there was none to be had. I tried multiple setting and nothing worked to get heat. I stopped and looked a the coolant in the system, just in case the cylinder head had a leak but the coolant was full. After starting back up I was able to get heat I then notice that the recirculate switch turned itself off. I thought that I was seeing things when it turned itself back on. It did this several times. At this time the check engine light went out.

Friday 7-14-2017 in the morning very low acceleration from the truck for the first 10 minutes. Recirculate button came on and would not go off no matter what setting the vents were on this was the case for the first 45 minutes. In the afternoon mostly fine except for the occasional recirculate coming on from time to time.

My mechanic now says he things the cylinder head may be the problem and says that it will take 22 hours to do the cylinder head and truck full of cash.

Give the bizarre behavior of the AC system does the cylinder head seem the most likely candidate?

Is 22 hours reasonable for replacing the cylinder head?

Why does the engine need to be removed to replace the cylinder head?

That was a long read. Any advice would be helpful.