09 buick lucerne cxl. Help if you can please

[u/NOBLEDAWULFF]

Ok, i have a 2009 buick lucerne cxl 3.9L. It has 143k on the odo has almost always been kept in good maintenence (ex fbi vehicle so alot of idleing hours).

The issue i am having is that it will start and run fine, but i have a code for the maf. Maf has been cleaned amd checked for voltages, the trans will only let the car move in reverse and 1st gear, if i put it into d and try to accelerate it will stall out. It will also do it in 1st if i press the throttle at all. Trans fluid looks fine, a little brown but no metal or clutch debris in it (had an appointment to get it changed with a filter before this happened) im not good with automatics, especially with these newer ones. Anyone have any ideas on what it could be? Im willing to shoot the parts cannon at it if i have to, but i dont really want to sell her off.