I think the Malibu has a sealed for life tranny, but im not positive.

Yep, No dipstick.

The red capon top of the transmission, drivers side, is the way you fill the
transmission, it is also the vent.

To check the fluid level (It is best to have the car on a hoist or on jack
stands) there is a plug on the passengers side of the transmission, just
below the transaxle shaft.

The car should be level, NOT running and the transmission COLD.

When the plug is removed the fluid should just trickle out, If you are
checking it when the transmission is hot or when the car is running, you
will not get the correct level.
The fluid should be changed every 50,000 miles, Dexron 3.

The transmission gasket is reusable and metal reinforced and should only be
replaced if it is torn.

Hope this helps.

I JUST FOUND OUT MY 2003 MALIBU HAS NO TRANSMISSION DIPSTICK. THIS
SUCKS. THE OWNERS MANUAL SAYS TAKE IT TO DEALER IF YOU SEE A LEAK.
DOES ANYBODY KNOW IF THERE IS SOMETHING FROM A PREVIOUS MODEL THAT I
CAN ADAPT. I FOUND A SCREW IN CAP ON TOP OF TRANNY, BUT I AM NOT SURE
IF IT IS A VENT OR A FILL AREA.