This is a really easy process. It just takes a step by step time. There's a photo tutorial online somewhere.
When I did it, it took longer than four hours, but that was because I was painting stuff along the way and wanted to make sure the stuff had time to dry. While you've got the core out of there, you might want to check the motor and possibly repaint the squirrel cage, the vent doors and such. You might also want to redo the linings if they're shot. Once you've got the box off and everything open, it pays to redo it all. Saves you from having to go back in.
Also, take the glove box off, but also consider prying the blower motor resistor off of there. I didn't and when I went to put the box back in, I beat the hell out of the prongs and nearly destroyed the thing. If you take it off, put the box in and out and then put the resistor back, you'll get better clearance and save yourself a headache.
1968 289 Coupe, 4.7L, 2BB, vinyl hardtop, gold metallic original.
I'm restoring a barn car into a fun ride, so all the help I can get is appreciated.