On 2008-08-11, wrote:
Help me, I am new to STI.

When replacing the cables should I get the non-stretch ones from
Aztec?

I don't know about non-stretch (some claim to be "pre-stretched"), but
it is worth getting stainless cables because the other ones do rust and
break rather quickly. Shimano cables are good. Also get the right size:
1.2mm diameter for gear cables, 1.5mm for brakes.

With my Dura Ace STI the chain clanks lightly when I am in big ring
and middle cog. It is adjusted properly for the limits. A knowledgable
friend recommended replacing the cables etc
I am looking at replacing the cassette, chain, and cables. Is this
all worthwhile?

I wouldn't bother with replacing the cables until they're broken.

Maybe you need to adjust the cable tension a little bit. Find where it's
clanking and decide if the front or rear derailleur is too far in or
out. It is possible one of the cables is starting to fray up a bit and
that is affecting things. See if you can get a look at it inside the
brifter. If that's the case then obviously replace it.

Replace the chain if 12 complete links measure longer than 12 1/16
inches. If they're longer than 12 1/8 inches, replace the cassette as
well.