Ok . You can syringe the oil out of the difs but you won't get any metal particles out that way or be able to check its condition. Take the covers off clean it out and rtv the covers back on. Use quality dif oil.
If near your gear selector levers it says QuadradrIve (unlikely) then that what you have and you need friction modifier in the axles only. If it says Quadratrac (most likely) then you don't need fm. Either way the transfer case is the same one and needs the factory spec fluid ONLY...mopar if you can find it (discontinued in the UK) Petronas other wise.
You are correct about the tc location.
If you hunt back to one of my early threads you will find a link to pdf versions of the CRD parts manual and factory service manual. Download it and just print pages as you need them. Would put link on here but can't do it on my phone. Cheers!
EDIT; Found the Parts and service manual link:
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