Hi there
If you're sure your CDX seats are memory and rear heated, then they would have been an optional extra on a CDX to elite spec so a lucky find. I've fitted 98 minifacelift elite seats to a facelift lower model car (cdx i think) so know some of the issues involved.
Firstly is your R reg GLS a minifacelift? i.e. do you have side airbags/solid headrests? If so, do your CDX/elite leather seats have side airbags? If you've got side airbags but your leather seats dont you'll never get the airbag light off without some ecu programming (unless you butcher your old seats, get the bags out and plug em in!). If you're swapping like for like, then fine. Also if your GLS has no airbags and your leather ones do, no problem (but obviously the airbags wont work!)
If everything's OK then you can proceed. One thing I dont know is if GLS already has heated front seats and electric height adjustment. If yours does then fine - you've got all the wiring you need up front. If your GLS doesn't have heat/electric already, i'm not sure if your wiring will be there, but it might be. Look under the carpet for the plugs tucked away somewhere. They connect to the seats between the seat and the door.
If your wiring's present the passenger seat is a doddle - just plug it in and it will work fine. When I did the mini-facelift seats into facelift car, there was different seatbelt pretensioner plugs used - so we just swapped over the pretensioners. Swapping like for like year seats should be just plug and play.
The drivers memory seat is slightly harder. Only an elite has the 20-pin rectangular plug that you will see the socket for on your drivers memory seat. This provides power for the memory module on the seat and signal wires to/from the mirrors. You dont need to worry about this plug and all the mirror wires, but you do need to power up the memory box on the seat. This is because all motors are wired up through that box. Unfortunately I've forgotten which pins on the seat need power/ground

. There is a photo kicking about somewhere that shows this - hopefully someone has it. Maybe try vxonline if i'm allowed to say that

! Once you've powered up the memory box and plugged in the normal seat plugs as per the passenger seat the driver's seat will move just fine. Memory function will work too, but not on mirrors obviously.
Rear seats are relatively simple. All cars have the wiring for the rear hear switches - you just need to fit the switches. However only the elite (or your upgraded donor CDX) has the little loom extension that contains the rear heat relays and seat plugs. There is a square plug under the rear seat insulation near the passenger side door area. This is where the loom plugs into. The relays live inside the hollow metal beam under the seat and the seat plugs exit from there. You'll only find the square plug near the door - you'll need to get the relay loom from an elite. You will probably find another unused square plug here too - if memory serves this is for the elite self levelling suspension loom - so get the right one (they're probably different anyway). Once you've got the switches and the loom extension with relays the rear heated seats are literally just plug and play - even mini-facelift into facelift.
Hope that answers your questions. Hope someone comes along with which pins power up the memory box!
Liam