You have an AODE trans , should be a electrical connector on passenger side of an slightly odd shape.
Check the lever for fitment in the replacement trans. Should fit if the model year is near correct.
Check tail housing for a large W cast on the side of each trans. You can not replace a AODE with a trans that has a W (4R70W trans) on it or the other way. The vehicle computer will see a ratio difference. 4R70W has different ratios.
Dont worry how old you are... it is the mileage on your body that adds up.