If it's anything like my son's 70 it's not too hard. There are four nuts on the outside(firewall) in the engine compartment, two on top two on bottom. The lower one closet to the engine can be tricky to get to. There are two screws inside that attach to the firewall. One about mid way between the passenger side kick panel and the tranny tunnel and one on top alittle to the right of the lower one. It makes it easier to access the top one if you remove the dash pad. You'll also need to remove some ductwork to gain access to things. The "suitcase" will then pull/fall off the inside of the firewall. Remove things slowly as thre are a lot of vacumn lines and wires. If you remove any wires or lines note where they go. You don't need to completely remove the box but you can again just note where things go. Then you'll remove the cover over the core and replace. Reinstall in reverse order and that's about it. One thing I might add is be careful when you put it back in, I managed to get a vacumn line caught between the case and the firewall so I had to losen it and get it out. I also found it easier to remove the pass side kick panel. Good luck, Pete