How many solenoids are in the transmission and what are they??

What is your question?

I recently purchased a 2006 Buick Terraza with 109,000+ miles and noticed it shifts odd. Sometimes my dashboard will shake and I noticed a little shudder when it shifts. I had a diagnostic check and they pulled a code p1811.(?)Max adapt and long shift. The description said 3 things cause this: worn clutches, low fluid, and a bad pressure control solenoid... Which they said was a GM only part. My fluid isn't low, but it isn't red either. Was also told worn clutches unlikely because of age. Some auto parts store ordered a transmission control solenoid. I am not sure if that's the same as pressure control solenoid. Carfax didn't show any transmission fluid/filter change and book says every 100,000 mi. Many questions... Are the 2 solenoids I mentioned the same? Are they GM parts only? How many solenoids are in the transmission? Any support or advice will be greatly appreciated. Thanks.