Damaged pulley/ belt replacement questions

[NaptownDub]

For refrence I drive a 2006 jetta 2.5. So while doing an oil change and spark plugs, I just happened to notice that one of the pulleys on the outermost belt loop, is damaged (see pic below). I have been keeping an eye on it for the past two weeks and have not seen any damage developing on the belt. How concerned should I be over this?

My questions are such;
(1) Can I buy this pulley by itself without the tension arm component?
Also, can anyone help me concretely find this pulley online? Maybe a part number I can use to find it?

(2) I figure while I am at it, I may as well change the serpentine/ accessory belts, considering I am at 64k and have never done so. And at that point in time if I am to change the belts, then I am considering doing an under-drive/ lightweight wheel (from ecs). Any comments on that?

(3) Can someone clarify the purpose of the two belt system? What does each belt power?

[Earlskey]

mine started fraying, I bought a replacement here:

http://www.ecstuning.com/Search/ES260692/ES260692/

Assuming you have the lightweight pulley from ecs:

http://www.ecstuning.com/Volkswagen-...-2.5/ES260691/


DIY:
http://forums.vwvortex.com/showthread.php?2631717

[eatrach]

To answer your question, yes these rollers can be replaced.
I had them replaced when I had the water pump, thermostat, belts replaced. These rollers don't cost much, but the labor is high; unless you can do it yourself.

My mechanic recommended that I change them. Said that he've seen some fail.

[NaptownDub]

I am confident in my ability to work on the engine, I have a jack, stands, all the triple squares and torx bits ill need. I suppose that while I am down there with the belts off, is it worth it to replace some of the other rollers? The car spent 5 years on pa winter roads and they appear pretty corroded. Is there a kit out there for oem or non-oem rollers?