Thanks for the comments from all.
I am aware that I will need some residual analogue instruments (ASI, Altimeter and compass) - I will re-use the existing ones - there should be plenty of panel space left for the ASI and Altimeter - the compass I'll leave as is.
How tricky is it to retrofit this type of kit?
Is it a specialist job or could a reasonably competent amateur do it? by following the manual (which seems quite comprehensive for the Dynon D 180).