Step 5 - remove the black pieces under the dashboard. There are 3 plastic rivets holding these on. Pull out the raised tab and the rivet will come out.
Now you can actually start at teh heater core.
Step 6 - remove the outer heater core cover. There is a great post on this on this site. With the seats out can carpet back there is plenty of room, but you have to lay on you bcak and make sure you have a good light source. You need a 1/4 inch wood chisel and nut drive toremove all of the mounting point. There are plastic rivets that you need to scrape off the head with the chisle. Just take it down until it is flush. Now you can pop off the outer cover
Step 7 same thing for the inner cover. Screws and plastic rivets. There is one that I could not get to without a swivel type extension on my socket.
Step 8 - remove the heater core by just pulling it out. There is a foam piece behind it. Still not sure what to do with it. It has a piece of paper that if I remove I could stick to the heater core, just like the new one I bought. This is where I am at for now. If ayone has any ideas on the foam piece, and whether the paper goes toward the core or away I would appreciate it.