You can simply import dxf files into CAM software which you can visualize in a CAD type environment for example top, front bottom bacl left and right views. You can also import 3D wireframes however I haven't done this.
You then have to apply toolpaths to to the shapes created by the dxf file.
This is quite easy an easy task but it may take you a few days to get the hang of it.
There are several variables and constants you will have to set up within the CAM software before you produce the G-CODE such as:
Tool dimensions for each tool your machine is to use, this is so that the software knows how far to offset the centre of the tool and position it in the Z axis (as all tools/cutters are different sizes).
The machining speed. (This may be tool Specific or may be a generic speed or a combination of both.)
Spindle Speed. (This is usually specific to the tool used and material to be machined
I havent used any CAM software for a few years so there may well be a package that is more automated and can create toolpaths from a 3D CAD model (especially for complex 3D >3 axis machining) , however I expect there will nearly always be some human input required when creating toolpaths such as direction of cut and order of cut (please correct me if I'm wrong) Its hard to get a computer to automataically prepare for every possible maching complication that you may encounter.
I have worked in the furniture industry so It was always important for me to decide which way a cutter would cut around a piece i.e clockwise or anticlockwise as it made a differnece to the cleaness of a cut due to the grain direction (which the computer could not automatically account for).
The software I have used was (Licom / AlphaCAM) this had the ability to show a virtual 3d model of the part to be machined. It would also show an animation of the part being machined, this was usefull but I wouldn't always trust it.
I would send the g-code file to a machine operator that used another program to control the machine, he could visualise the g code on a screen using 2d views, he could then make small changes by clicking on the toolpaths and changing settings.
A good CAM program is one that does what you require. It would depend on the complexity of the parts you wish to produce along with other factors like the limitations of your machine.
I would check out some of the different CAM package websites. There is probably a lot of advice on this website showing peoples personal preference in other forums on this website.
Hope this of use to you.