that is impossable to answer. life of belt all depends on how much the engine is run
How long will it take to replace a belt tensioner unit and serpentine belt in a lexus 1996 sc300?
No, an accessory belt is not considered a serpentine belt. However, a serpentine belt is considered a specific type of accessory belt.
The serpentine belt would be the same as the accessory drive belt.
Yes, as long as there is no damage to it
The serpentine belt is a long belt on the front of the engine. The belt goes over a number of pulleys and powers many things such as the alternator and power steering all at once. The twisting and turning through all of the pulleys like a snake is how it came to be called a serpentine belt.
Serpentine Belt Diagram ML320
Serpentine belt, no. Timing belt, good chance yes.
If the alternator belt is the same belt as the other accessories, yes.
That I know of, there is NO serpentine belt, unless you are talking about the the Timing Belt (hardly serpentine, but anyway), it has a belt tensioner, not automatic, though.
Loosen the tensioner pulley. Slide the tensioner pulley to the right. The serpentine belt will come loose. Remove the serpentine belt. Reverse the process to install the new serpentine belt.
Depending on quality it can last 5 years and more, but it's not guaranteed because the life span depends on in which conditions you usually drive.