Replacing Heater Core Need Instruction

First, I would download a copy of the Rave manual. There are a lot of steps involved in removing the dash. Search heater core and I am sure you will find a few threads on this topic. The joke is that when they built the RRC and Discovery(same thing) they started with the heater core on a rotisserie and then built the rest of the truck around it. This is not far from the truth. Expect a full weekend in doing this replacement. In a nutshell, you will have to disconnect the battery, remove the glove box door and fuse panel door, drop the steering column, remove all the trimmings and unplug/disconnect everything before pulling the dash out...Someone needs to make a powerpoint slideshow of this job as they are becoming more common as our trucks age...When I pull the dash out of my parts truck I will document it for everyone, but that is a few months away yet. Take your time, you will be alright...

I did similar on my 2000 discovery 2. Big job and numerous procedures such as the removal and re install of the dash assembly are best to be a 2 person job took me about6 1/2 hours in my driveway at those. Not a job for the faint if hart. But also not anything really high tech.
Read up and have fun if you feel up to the challenge ---- or pay someone else $1000 bucks

A google search may turn up the steps from a guy who claims he can do it in 30 min or something crazy like that. I can't remember which forum is was on. Might have been DWeb.
It's a real pain, so I would suggest considering replacing the pipes as well. That's what actually rotted on mine.
Also get a few adapters so you can attach a garden hose to one pipe and cap the other one.
I assembled mine (used a little RTV on the o-rings for even more sealing, installed it to make sure the pipes were aligned right, then pulled it out and hooked the garden hose to it to make sure the seals didn't leak. It's such a pain to replace I didn't want to have to do it again. But most people just install it and don't appear to have any issues. I can be OCD at times.

There is a way you can cut the pipes and slide the heater core out without having to remove the entire dash. Most shops will take this shortcut to bank the extra shop time. I think LR charges 18 hours or something like that for this job. Definetly worth doing yourself and saving the $100 an hour in shop fees. Mine has not puked yet, but I know others who have done it personally and it is not fun, but not impossible either. There is a very good reason for replacing coolant every few years!

I have done this myself a few months ago, and yes it is a big job but not difficult just need to pull half the car apart to get to it lol I did not have fun refitting the speedo cable.