We need to retrieve the spring. Once again, this is simple but don't rush or you'll scatter more parts everywhere.

I found it easiest to remove the spring from the door. This does involve flipping over the shell, hence the additional warning to watch for loose parts.

The door hinge is a small plastic nub in the shell that locates into a large hole in the door (see red circle), a little leverage with a spudge should free it.

The sprinf is retained by a sturdy stainless pin (Shame that the other end was not so well thought out.) poke the end of the pin free enough to slide the spring loose.

You can now attach the spring to the repaired lever by hooking the open spring end through.

Finally, you need to offer the spring back through through the hole in the case and with a pair of tweezers or a hooked spudger, pull it back onto the metal pin

push the pin back home to lock it all in place.

slot the cover back over the hinge nub.