Heater Core - this what I have to do?

[BobRitts]

1972 K10 LWB w/AC. So my heater core finally gave up the magic steam and has been poisoning me all day... It's been real cold so I had the heater on for a while, and I think I've got a quart of antifreeze in my lungs now. Dripping on the floor too...

From the looks of it I have to:
1) pull the box from the inside, half dozen 3/8 or 7/16 sheet metal screws and maybe some little pins or something, so I can get to the core itself.
2) pull the entire heater box and fan housing from the engine bay, including probably taking out the inner fender well, so I can get to the hoses that attach to the I/O of the core
3) put it all back together.

Is this the right way to replace the core? Man that looks like a lot of work... and my garage is about 0.5 degrees warmer than the outside air.

Thanks in advance!