Is $1200 for adapter housing gasket,pressure control solenoid&engine mount fair? on 2006 Chevrolet Impala

Took car to dealer because I had a small leak and I noticed car seemed to be shifting a little rough. They told me the adapter housing gasket was BIG job and it would be almost $300 of the total. The pressure control solenoid had to be replaced immediately or transmission could fail--pricetag of $700. They're supposed to be sending codes but haven't seen them yet. Are they taking advantage of my lack of knowledge?

Asked by for the 2006 Chevrolet Impala
no I would have provided u all codes sorry to say but look at it this way a doctor takes his car to a mechanic and complains your fee is more per hour than we get for medical care yeah doc mechanic replies but your models haven't changed since Adam and Eve and we have to stay up to date on new models coming out every month.
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P1811 max adpt long shift (this solution was replace pressure control solenoid & service transmission for $700 + tax.) The other was found oil filter adapter gasket leaking (solution was oil filter & adapter housing gasket $220 + tax.) Then had to add oil & filter change for another $36.34. Also found engine mount broken (add another $230.) Vent evap vent solenoid stuck open ($130.) The only actual code they gave me was the first one I listed. I'm not familiar with how much labor is involved to replace PC solenoid and service transmission but must be enormous if labor cost is almost $500 of the total. Please advise.