Help. Can I replace the alternator on my Discovery TD5 myself?

Evening,

My 2001 Discovery conked on the M25 yesterday and the AA tells me it needs a new alternator. I'm not too mechanically minded so I called a mechanic recommended by a friend. Said shifty mechanic turned up this morning with a new alternator but after looking under the bonnet said "I cant do this, take it to a Land Rover garage you have to take the manifold off etc etc, blah blah spanners and stuff and so on........."

Can this be done at home? Does anybody have a how to guide? (I used a fantastic one I found on here to replace diesel pipes..) or can advise a good place to take it for repair? I'm in hornchurch near Romford. It wont run (or will it with a charged battery?) but I have a trailer....

I apologise if this has already been answered but I have looked for an hour without finding what I need.

Thanks in Advance

Ash

I cant help other than to say post it in the disco section..more chance there..