...and the hits just keep on comin'...so now getting a faint coolant smell when using heaterwith 130k on the odometer, probably time for a heater core replacement...found a decent product online..swedish auto parts...and have watched several online videos on how to do this procedure..doesn't look too overwhelming..my query...in none of the videos did they mention changing or change that intermediate-through the firewall pipe and plastic assembly...should I order this, and plan on changing that out as well??...certainly willing to pay if I need it, but no way of knowing until I get in there...

I would get the $49 heater core seen on Ebay. The quick disconnect at the firewall should last a very long time, it is not a moving part.

What the videos don't show you: when installing the new core, attach the core to the coolant pipes FIRST, with new O rings of course. Then screw the core in to the plastic case to hold it in place.

Make sure you have emptied the radiator about a 1/2 gallon, and have a water tight plastic bag to catch the coolant that is in the 2 pipes and core.

I use a Tshirt to filter the coolant that is poured back into the overflow bottle.
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Keeping it running is better than buying new

Sorry to hear it. One of my least favorite jobs. Leak to begin with got the carpet all messed up. Space under the dash is awful. Was hard to wiggle out. More spillage when it did finally come out. Was not 100% sure the o-ring seal and tube was sealed well enough (at least it was and didn't have to do twice) Used my carpet cleaning machine about 4 times, bucket of rags. I like the PCV job better, even with fuel rail and manifold. Or, radiator job.
Still would never have wanted a garage to do. Not much in the way of complexity at all. No through the firewall messing necessary.
G-luck
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Farewell 'black manta' ('97 850) Hello 'rocket sled' ('06 V70R)

again to you both...many many thanks..

Tom