I have been reading about a lot of problems setting up the gear linkage on Laguna 1's after either the clutch or gearbox has been changed.
The gearbox on my Lag1 Ph 2 Dti got stuck in 3rd gear a few weeks ago,and I had to change both the 'box and clutch assembly.Whilst doing this I found a way of disconnecting the rod that runs from the gear stick to the gearbox without altering the adjustment.
If you have a look at the (rather rudimentry!!) photo in the attatchment,you will see the nut and bolt that most people undo to remove the rod from the 'box(marked 'A').This is where the adjustment is made,and is best left alone.If you pull back the protective rubber gaiter (marked 'B')from the end of the rod that connects directly to gearbox,you will find another nut and bolt(marked 'C').If you remove this,then you are not going to change the rod alignment,and you should still have the full compliment of gears when you refit it.
The rubber gaiter is a bit of a pain to remove and refit,and you have to be careful you don't loose any of the rubber/plastic bushes that are held in by bolt'C',but it is a hell of a lot less hassle to do this than it is to spend hours trying to adjust the rod so you can get all the gears properly!!
Hope this helps someone,and sorry for the quality of the picture!!