It's actually sort of a fun job replacing the heater core.
It's a great opportunity to clean up wiring back there, clean the carpeting under the seats, dust off things, flush your coolant, etc.
I've never done our style, but several foxbody's.. it's the same deal. It's sort of neat because you get to see parts of the car you haven't ever seen before, and then you can come on here and share your knowledge with other people who are about to go through it.
Really, all you do is drain the coolant, disconnect the lines at the heater core, remove the seats for working room, remove kick panels, lay down some towels, remove the radio and wiring, loosen a couple bolts to let the steering column drop down, remove the nuts/bolts securing the dash to the firewall, remove the top bolts, have a buddy help you slide the dash back. The hardest part for me both times was finding all the bolts. If you have a ford service manual, or somebody can get you a screenshot of the bolts, it'll save you tons of time.
You can just let it rest on a piece of wood, or on the shifter if you prefer, then you get a work light and stick it up under where the HVAC box is, cut a space in it to pull out the heater core, or if you've discharged the a/c, just disconnect the evaporator core lines, and unbolt the entire HVAC box and pull it out. That way you just remove the bolts holding the heater core panel on, and don't have to cut anything. Put some soft drying RTV around the base of where the heater core sits, set it in, and let it dry for a few hours.
While that's drying, you can clean your carpets up, find some nice seat covers to put on, blow some air through the HVAC box to get the leaves and crap out of it, poke around up under the dash and checkout the horrible wiring mess, etc.
You and a knowledgeable buddy or 2 could have it done in one day, but I set aside an entire weekend for my foxbody.