Hello everyone!

I have a 2.4L 2012 Chevrolet Malibu with 187,000 I got for $700.  After changing the damaged water pump it has been a reliable vehicle for a few months now. I topped up the automatic transmission fluid when I first got it (I have added 1500-2000 miles since then). While the fluid looked dark when it poured out of the check port, it did not appear jet black nor did it include metal sparkles.  Now that I am planning to do some more maintenance, should I change the A/T fluid?  Should I replace a few quarts and see how the transmission performs?  Currently, it sticks a little bit when entering third gear, although I am pretty sure this is down to a sticky shift solenoid (apparently a common issue on this transmission).  I do not feel any slipping.

Thank you!