W126 Leaking Heater Matrix-radweld,bypass it or DIY replace?

[matsmith]

Looks like my matrix has had it! There is steam on the screen when the heating is on. Also I have noticed water leaking from vent between two front seats and centre console, making the rear passenger well wet.

I bought this car for very little as my fun for the weekend. Paying a garage to replace the matrix is probably going to cost more than the car is worth. I see I have three options:

1. take the dash out and replace the matrix myself. ( I have not been able to get a haynes manual and imagine this is a difficult job)
2. By-pass the matrix from the bulkhead and have no heating!! Perhaps get an electric heater for winter! If so which pipe does what behind the bulkhead??
3. Try putting in rad weld or similar sealant in the system. But can that fix the matrix?? It's not pouring out. I did 50 miles (two hours) driving today and I lost 1 litre max of water, so if the systems under pressure that must mean its a fairly small hole.

Has anyone tackled this job in their W126?

Can anyone direct me to a source of info on how to remove the dash?

I would really appreciate any guidance on this subject.

Thanks.