Welcome aboard! Re: the solid nav...Why would you do this? Does the existing diesel need replacing? I would think you will take a major hit on the value of your boat if it is no longer "cruising" and merely capable of short runs under power. If you want to start a new thread on this I think it would be interesting to understand what you have found in your research and why you have made this decision.
As an aside...one of the Lagoon electric 42's stopped by here the other day and they have been out cruising for a year since I last saw them. They indicated they were NOW happy with the perormance but they had a lot of issues over the last couple of years getting things to work right and making lots of changes to the original stock boat. They had nothing but high praise for Lagoon and the Catamaran company who have both stood by them and worked hard to make things right in what they new was kind of a guinea pig situation.
No longer posting. Reach me by PM!