The oxygen sensor on the 1999 Oldsmobile Cutlass Sierra is located on the lower exhaust. If you need to replace it, they are available for about $20 online.
Follow the top radiator hose down to the water outlet on the engine; the stat is in there.
You fill the radiator through the overflow tank.
Starter is always going to be on the bottom rear of the engine connected to the flywheel.
In the fuel tank
dextron / mercon type 2
The 1999 Oldsmobile Cutlass OBD 2 port is under driver side dash left of steering column
The paint code is located in the trunk on the platform that over the spare tire. That's where you will find it usually three numbers and one alphabet.
Between the engine and firewall labeled TRANS. Under the Air Filter/ Intake box there is a red cap on the transmission for putting in fluid. There is no dipstick that I know of on a 1999 Cutlass w/ 3100 "J" motor.
Begin by loosening the tensioner pulley on your 1999 Oldsmobile Cutlass. Put your serpentine belt around the pulleys. Tighten the serpentine belt with the tensioner pulley.