Here is what you will get into

Flickr: Landroverdude2's Photostream

 

it looks much harder than it is, you remove a couple dozen bolts and then you put them back in.
if your not sure there is a DVD out there "in search of" or something like that It walks you threw doing head gaskets on a disco.
Buy it, watch it and if you think you cant do it after that fine, but once you see how simple it is you will do it and be proud that you did.

 

In Search of the Experience

DVD orders « in search of the experience

There also appears to be a decent amount of disco specific youtube vids of HG replacement.

 

Just as an aside and personal experience. Four months ago I used Rislone (Bar's Leak in the US) Liquid Copper Block Seal Intake and Radiator Liquid Copper to help solve a valley pan gasket leak. It worked a treat. Last week I replaced my water pump and took these photos.

As you can see there are no deposits in the water pump or block at all (the blackness in the pump is just mild oxidation of the aluminum). There were no signs of the copper that you can see in the additive. I also replaced the Thermostat a couple months ago and it had no deposits in it either (I only replaced it for the 180 Grey Land Rover Thermostat to lower my running temps, the original was working just fine).

Just thought I would dispel some myths.

 

Based on your description, I doubt that the cause is a cylinder head gasket failure. I bet that the leak is caused by the loose intake manifold bolts. They get loose because of the V8 expansion cycling every time it heats up. They leak at the rear where the crossover pipe is.

 

Thanks guys, I appreciate the good advice. I'll let you know the outcome.