My idiot neighbour broke one of my conifers when he came home drunk one
night (I presume that he fell on it). What's the best way to replace a
single tree? It's part of the border between our gardens. They're quite
densely planted.

Do I just dig-up the roots of old conifer and plant a new one? Are mature
conifers expensive? Are they difficult to plant successfully?

Should I buy a mature tree or a young one and let it grow to the same height
as the existing trees?

Cheers.

Bobby