How long will a timing chain last on a passat with a v6 engine

Belt - quieter.

For what car?

autodata book describes volkswagen passat 2.8 l v6 30 valve --1998-06 as having a belt
it is identified as an intereference engine which means that valve damage will occur if the cam shafts and piston are not set right and are moved with out care being taken

There are several engines in a 2000 Passat, but none of them have adjustable timing that I know of. The main thing one needs are camshaft timing marks. If it is the 2.8 V6, I won't even begin to start because you need to rent cam position tools, and you need a book.
The Vr6 is a chain and you don't set cam timing normally.
The 1.8 turbo looks like the link, I believe.
http://ww2.justanswer.com/uploads/DubAutowerks/2009-12-03_210857_mk3timingmarks.jpg

Don't quiet understand your question...but here's some insight.

The chain is under the valve cover/s ( 1.8t and some 2.8 V6.) and drives 2 or 4 cam shafts.

If it is the VR6 engine then the chain is in the front of the engine.

1.8t has seals on at cam sensor at rear of head and seals at front for crank and cam. To install it needs belt removed for front seals. 2.0 gas engine same except no rear cam seals.

All oil seals are now Teflon and a new instal procedure must be followed. Briefly : Installed dry...allowed to sit 4 hours before engine started.

Post again if this does not answer your question. We need year and model to give you a definitive answer.

Reading Topic: Timing Chain?? Both the 4 cylinder and 6 cylinder use timing chains. These chains are pretty much service free and should last the life of the vehicle. Borrowed from http://forum.mazda6club.com/mazda6-atenza/121169-timing-chain.html

the timing belt or chain...which ever you have...
a transmission oil change...every 3,000 miles or 3 months you need an engine oil change...so check that...
the spark plugs and wires,change the rotor if it hasn't been changed for a while...and check if the radiator needs flushing...
Good Luck!

The 2002-2006 Camry received the next generation 2.4L 4-cylinder engine (model 2AZ-FE), which combines decent power with excellent fuel economy. This engine does not have a timing belt, it has a chain that does not need to be replaced.
The second choice is very smooth and powerful 3.0-liter 24-valve all-aluminum V6 engine.
Starting from 2004, the 3.3-liter V6 DOHC VVT-i engine is available on SE V6 model.
Both, the 3.0L and 3.3L V6 engines have a timing belt that must be replaced at certain interval

need to repair

The 3.0 and 3.8 V6 have a timing chain not a belt, lasts life of engine in most cases