I did this in October last year. As I sail on Windermere and long distances are not required, I bought an electric outboard. I looked at Torqueedo but settled on the ePropulsion 1kW with a 1.2kWh battery, slightly bigger than the Torqueedo and with a smaller drive unit to fit through the well cut-out.
I have been entirely happy with it as quiet enough to use in the cockpit. Another major benefit is the absence of diesel or petrol smells and the weight without the battery makes it much more user friendly than the 6hp petrol on our dory. Even the battery is light enough to carry away for overnight recharging.
The range varies with speed but seems capable of 10 miles, the full lake length, if we ever wanted that, and can push us at 4 knots for shorter periods. I have a solar panel, stuck to the cabin roof with Sikaflex, for which ePropulsion do a special charger and keeps the battery full out on a mooring.
The outboard lives happily under the cockpit on a plywood board that replaced the engine.
I had a pair of old 100 amp hr batteries as back-ups to increase range. They worked via the ePropulsion solar panel charger but not being needed they came home again.
The Dufour instructions say the well is bonded in. I confirm that ours was. I cut though the sunken area, leaving a small margin all round, which exactly fits the drive unit. It cut with a jig saw from the top as a single piece which I then attached to a timber frame so it goes back into the hole as a blanking plug when sailing.
Also needed was a thick plywood engine mounting board which is bolted to the front of the well and trimmed to fit the lid.
The whole set-up has cost more than a petrol engine but now has no fuel cost and is much more pleasant. We did try the 6hp petrol outboard but the weight was too much, the noise excessive and the additional speed trivial. The big propeller on the 1kW electric probably makes it similar to a 3hp petrol engine.