R&R heater core?

[aaalbedo]

I have a 2002 4.6iS 165k miles with an apparent heater core leak (strong antifreeze smell in the cabin when warm). But the carpet is dry and the windshield is not even greasy, so it's either a very small heater core leak or it's coming from elsewhere. I've searched the forum so I know what's involved in replacing, but I'm not entirely sure it's necessary. So two questions:



What other source might there be? There are no apparent leaks around the engine but I'll take a closer look today; might it be sucking the smell in through the cabin air filter?



And if I do decide to replace the core, what other things should I do while I'm there? I know the whole dash has to come out, and I already have the core, a new blower fan, FSR, and HVAC air temperature sensor. I tend to be a long term owner and prefer to spend the money to replace what ain't broke while I'm there rather than doing the job of removing the dash again later. I see the hard pipes that pass through the firewall are available; is it recommended to replace those too while I'm there? No signs of issues with those from the engine bay side.