dpot,
Took a quick look at what you posted.I suggest you take a look at the LazyCam manual.
Note that LC will default to a positive Z=1 for the rapids on import of the dxf.
How are you planning to cut out the parts of the plane? I think that the layout was meant to use a knife
to cut them out as there is only 2 mm between some of the lines.
Note that if you wanted to cut everything out all you have to do is select the layers you want to machine and define the cut parameters for those layers. If not LOL, as the entities are scattered into diffferent layers.
Have Fun,
RICH