There is a dipstick on the transmission to check fluid level, do it with the engine started and shift from P to L and then back to P, check fluid level - it should be at the marks hot or cold depending on the transmission temperature.
If your transmission is slowly engaging D - you have a stuck piston on the first clutch or your valve body is starting to jam up with dirt or transmission pieces. If your transmission has forgot to engage R - you have a swollen plastic reverse piston - need to remove tranny from car to rebuild - This is very typical in cuore Automatic