Swapping G8 Halogen Under-cabinet fixtures for LED

I’ve got 6 under-cabinet fixtures that use G8 20V bulbs. I’d like to swap them for LEDs. I’ve tried putting in bulbs but there’s some difference in the voltage load and there’s a lot of flickering. So my next step I guess is to swap the fixtures. They’re direct wired around the perimeter of the kitchen, controlled by a switch. Should I expect this to be somewhat straight forward (is anything? 🙂 )? Should I expect there to be more to swapping one for the other than connecting the new one up to where the old one was, moving the old fixture wire connection to the new fixture wire connection? I haven’t opened one up yet but I assumed the fixture is connected to the wires in the wall via some wire nut or similar.