I think I've read that you can swap them. From dim and distant memory, you get...
Time elapsed since trip reset
Miles elapsed since trip reset
Average speed since trip reset
Average fuel economy since trip reset
Expected range on remaining fuel (based on average fuel economy since trip set.)
You also get two trip memories. Memory 2 can be reset independently of memory 1, though resetting memory 1 clears both of them.
Like the Lag II, the fuel functions stop working just when you need them the most - i.e. as soon as you go onto low fuel. Also, there's no instantaneous fuel economy. I know it doesn't apply in your case, but I vaguely recall the fuel functions not being available on the earlier diesels, even when they had the trip computer as part of the factory spec.
But owners of the Laguna II are probably still wondering "Why is the trip computer on my later model so crappy by comparison?" I know I am
The earlier dash had the odometer separate from the trip computer and remembered which display it was last on when you turned off the ignition. The later ones have the trip computer merged with the odometer (the space prevously used for the odometer is then used for the gear selection indicator on the automatics.) They always revert to total mileage when the ignition is first switched on, so the earlier dash is better in my opinion.