I've also heard that they stopped putting them in the cabins at some point... don't really know when they stopped (ask a local dealer what years they made them in).. From the description, it seems like the radiator thing you saw was prolly the heater core... JMO!

In my truck(s) there is like a one inch wide piece of plastic under the passanger dash that has a screw in it, you pull the screw and drop that piece... that piece holds in one of two filters... you pull the one out and then reach in and slide the second one over and pull it out the same slot... you replace in reverse... It costs like $12 for both and took less than five minutes start to finish...

 

they stopped in 03

 

ok so they still have them in the 03's or they dont... i had to replace the blower motor relay and figured since i had it apart to change them... there isnt anything there to unscrew on mine...

 

It's not hard to figure out... This is also speaking from my experience of my 1999.5 and 2001...

You unscrew (3 screws) the cover that protects all that stuff under the passenger side dash (I wanna say 7mm socket maybe)... There is a (about 3/4" wide) "L" shape strip of plastic that has a hex screw head showing (obviously attaching this piece)... Pull that screw... The other end of this cover slides into a slot... Once that piece is removed, pull your filter out, reach back in and slide your other filter and pull it out (would not hurt to vacuum what you can inside the housing)... Replace new filters in reverse...

It's pretty much common sence and easy to do... If you have filters, you will understand all this, if you don't have filters, then you won't have a clue what i'm talking about... It takes as long to type this as it does to change them out...

Hope you figure it out...