It is a while since I did this myself but had no problems. You need to remove the plastic trim/shroud around the tailgate locking button, (it just pops out if you lever gently all the way around it),remove all trim screws from the bottom edge (I recall just a turn and they pull out) and then you are ready to rock and roll.
The last remaining leap of faith is to give the door card a firm thump (or a series of thumps!!) upwards to release the metal prongs that capture the card along the top edge.
Not the most technical of explanations sorry!
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K