Welcome to nym! It will most likely take around 10 hours to do that. About a year ago I replaced the heater core in my fox and it took about that long. I found a pretty good write up of how to do it, had to figure some stuff out on my own, just took a while to do. If it wasn't your dd, I would just start removing everything to take the dash off, to get to the box and change the core. The dash probably won't have to come all the way, just enough to reach down there and change it. I would also get little plastic baggies to put the screws in and label the bags with masking tape.
I'm not quite sure how the sn95 interiors are set up, but I had to take the center console out, drop the steering wheel, take the gauges out, the hvac controls, glove box, then all of the screws holding the dash on.