my matrix is all done and dusted, i must admit that i have an overwhelming sense of pride for doing it! i have some photos to upload later... thanks for this tutorial, was a life saver! a few points for anyone replacing their matrix:
1) the job is one of 'point of no return' dont start it and give up... its heavy job but is easy, only time consuming.
2) dont be too light handed, the dash is pretty solid
3) the 3 nuts holding the heater core on 2 are above the exhaust flex behind the fire proof cover and one is next to n/s shock again behind cover (there are flap cut outs but hard to see)
4)disconnect the hoses from the matrix as its difficult to get it out with them still on (i disconnected from engine first but then from matrix end)
5) don't bother trying to remove the whole heater, just undo the silver clips holding the two halfs together, there are some on front, top, below and behind so its a task in its own but easy with patience and small screwdriver
anyone who needs it doing or needs a hand i am willing to help, its a weekend job and does help having someone whos done it before with you.