Having spoken to Boeing and the British Army on this very subject, the most likely scenario is that an undisclosed number of the 66 Ds would be 'remanufactured' to Es (new airframes, but with the old engines, MTADS/PNVS, fire control system etc). How many has yet to be determined (or at least announced).
It's win-win really, as you're essentially getting new aircraft but at a significant fraction of the cost (the expense is primarily locked up in the parts and systems you're cross-decking)
You've got that wrong as that's the last thing we would want to do. Keep the airframes and ditch the engines is what we need to do. The airframes would be zero lifed after the conversion and having the RTMs means we have our own bespoke software which costs (wastes) us millions of pounds every time we have a change. Full FMS buying AH-64Es direct from Boeing is by far the best option. Oh and the step change in capability between the two is enormous.... and trust me I know quite a bit about them
