There is a YouTube video of Sleipner installing a retractable thruster. Covers the mechanical part pretty well and it ties in with the installation instructions well too. The instructions are very good.
We have a retractable on our 405. Being retractable allows it to go well forward where it has greatest mechanical advantage on the pivot point. It was on the boat when we got her.
The membership association for owners of Dufour Yachts