Where do I go to find out how to replace the heater core in my 93 Dodge Spirit

Update-I'm finally done. Turns out I did have to take out the entire dash assy. I left the AC lines connected (on the right side) and loosened up the heater box. There are 4 nuts on the engine side of the firewall to take off and one hangar inside on the right side. Anyhow, I pulled the heater box back just enough to get to the top of it, used a hacksaw blade to saw the top about 12" from the left side. This gave me just enough room to pull the heater core out and install a new one (it was really nasty). I reinstalled the top and used some RTV glue where I sawed it. Put everything back together and it all worked just fine. Bottom line is I did not have to recharge the AC which would have cost me over $200 here in California.

Total time for the job - more than 8 hours and I didn't even break anything.