I recently changed everything other than the cam wheels - on engine strip down they looked fine. Mine was a 2007 159 Q4, so pretty much the first series Cadillac engine before they had two goes at sorting the problem.
Hopefully attached is a full list of everything I bought from GM Parts Direct. I bought a lot of things I wouldn't necessarily buy for any other car - but having spent two days getting the engine out (originally to do the output bearing to the rear drive porpshaft) I didn't fancy having to do it all over again if something leaked or failed. My postage was cheap as I had it sent to one of our work places in the US, and shipped it internally from there - they wanted over $200 to ship direct to the UK.
Bought the water pump from one of the UK internet places as they claimed Valeo - and it was when it arrived ;-)
I removed and stripped the engine first - got the part numbers (all GM) from the actual parts and went from there - a few were obsolete and needed a bit of seaching to be sure the replacement was correct.
Downloaded various engine guides from here:
*** FAQ - DIY - Guides - How-To - Manuals ***
and picked the relevant one (I forget which for mine) - genuine GM instructions - that were wrong on a few occasions - instructions to fit guides or chain wheels, then something else - and they really meant the something else first as the second bit wouldn't fit with the first in place - but easily sorted.
Watch fitting the final chain - the lower idler sprocket jumped a tooth unless I held everything in place - not really noticeable either as it did it. I'm sure that has a lot to do with when you read people having a misfire on start up.
When I got all the new bits, a close inspection revealed my chains (I did it as the engine was out, rather than an indicated fault) were still pretty okay compared to the new ones. The guides were close to the end of their life though. Interestingly the replacement guides, all genuine GM, were totally plastic - the same wear surface clipped in the same way to the carrier component, but the carrier was plastic rather than the original alloy.
My only problem was on todying up after sealing the engine up at 11pm on a saturday night was wondering if I really had torqued the second ilder bolt up . . . by 12.15 I had opened it up, checked (I had), cleaned, resealed and got it back to where it was at 11 ;-)
I sorted my going rusty subframe out at the same time.