I did the heater core over the weekend without removing the dash - thanks for the help and also this thread:
http://www.discoweb.org/forums/showthread.php?t=90937. I have a 2004.
Removing the dash supports on both sides of the passenger footwell allows for the dash to be pulled out of the way. You can then remove the blower housing and access the pipes and core, which slides out after the pipes are disconnected. I used a long screwdriver to gently pry the old core away from the heater pipes. I may have bent the pipes some getting them out of the way, but I was able to line them up and tug again to realign them. Getting the wrap around clips to work was a big pain.
I did the whole dash with my '93 RR and was hoping to avoid that nightmare. This took about 6 hrs.
I had my daughter start the engine long enough to push the air out when reconnecting the heater hoses. The weird thing was the lower pipe is the out and the top this in. Seems counter productive to removing air. On the top of the engine the pipe closest to center is in to the heater core and the pipe closest to the fender is the out.