Opted for the Heater Core C-Section
I decided to post about my project because it feels like I just passed the summit and it's all downhill from here.
It got to the point in the project and the weather that I needed to move things along a bit faster.
I used a size 16 wrench rested on the old heater core and a hammer to remove rubber hoses. Then I grabbed a dremel and cut around the top and front to clear space to tilt the old heater core forward and slide it out. I had to go back a few times to smooth out the sides so it would slide out. Not the cleanest job, but still pretty fast.
I'm putting in a new motor, resistor, and heater core after I get a few more parts (cushioning for the core so it doesn't rattle, and a replacement screw for the resistor). Then I'll use Silicone Gorilla sealant and aluminum hvac tape to put the box back together.
Just another 20 or so hours to go!