You have to remove the console, glovebox, the metal support underneath it and the blower motor. There are also two metal brackets in the passenger footwell, one on the left, right by the heater core, and one on the right. You need to remove the right side panel to get out that bracket. Then you can take the bottom of the dash and pull it up & out far enough to slide the heater core out.
The actual heater core removal was pretty much the way it's described in the RAVE. It won't come out all the way until you remove the flanged hoses going to it, and they are a BOOGER to get out.
When I put it back together, I used flexible heater hose & clamps to make it a little bit easier. I just left a couple of inches of the metal hose coming out of the heater core and maybe six inches coming through the firewall. (As previously mentioned, one of the hoses got mangled on the way out and I didn't trust myself not to do it again trying to get it back in.)

 

Follow-up:
Everything was going fine until a couple of weeks ago. Something started leaking again! Unfortunately, I wasn't even home at the time. (Been away for work & just returned yesterday.) I was able to walk my gf through the process of bypassing the heater core to make the truck driveable until I could figure out what's leaking. (Again.)
Problem is now the truck is running too hot, bordering on overheating! Temps were finally under control in the 190-200 range with occasional spikes up to 212. It had been like that for months. Now it's going into the 230 range, panic time. Does the heater core really have that much effect on the cooling system?

 

Bump. Anybody?

 

If you blocked the heater core lines, instead of "looping" them to keep coolant flowing in the pipes that would be a problem. If the main radiator is partially clogged, or greatly clogged, then the heater core is also playing radiator. Check main rad warmed up to be sure lower are is not 10F cooler than top rows on the core.

 

The lines are "looped." So it does sound like a rad problem, I didn't think the tiny heater core made such a big difference. Thanks Savannah!

 

It makes a difference if you only have 50% of main rad from sludge.