Well, I'm interested in what tutorial you've been following.  Looks like you've been deiting a box object to fit as a fuselage.  Personally, I think that's sort of a bad idea.  I don't mean any criticism, but it is much simpler to use a cylinder and then shape it.  Makes for a much more uniform fuselage.

Why don't you try the tutorial found on the FFDS site?  It worked wonders for me, at least starting out.  I would also suggest that you try to keep the poly count to a minimum.  I generally have between 1300 and 1500 for a large aircraft's fuselage in the beginning.  By the time I have finished it, the fuselage has between 25000 and 35000 polys.  It won't seem like you have very many until you actually check the specs.

I would also suggest you try making the seperate parts of the aircraft (fuselage, tail, wings, cockpit, gear) in different scenes in Gmax.  This allows you to edit without everything on the aircraft in your way.  I tend to use this method just so I can keep all my parts straight.

And one more tip: save different versions of the scene you are working on constantly!  Like if you are working on the fuselage, name the first one fuselage01 and then make a few changes and name it fuselage02.  After awhile, you can see how this will help you out.  I can't count the number of times I have screwed something on the aircraft up or been unable to reopen a file after a certain change.  Backing up always makes sure you have a spot to come back to that doesn't require remaking days or weeks worth of work.

Keep it up!

When deciding on the model construction consider how and which textures will be applied ie which sections will be suitable for applying textures from the top or the side and what the "edges" will look like.
On the YAS Spitfire series, I had similar problems when the squadron markings were applied to the fuselage, they overlapped onto the fairing ( as in real life!) I therefore redesigned to find a compromise shape for the fuselage and the fairing to give better/ easier texturing.

To get maximum detail on the model consider separating the wings at the nominal fairing line and then the texture file for the bottom of the fairing and included fuselage will be much cleaner. Also around the tail, make a part to include the tail down to the line of the tailplane only. You can then use a full side fuselage texture through to the rear of the plane.

A separate part is recommended for the top of the front fuselage. it's too flat to accept side texture. Do the wheel wells and rear wing edges as separate parts also to prevent the dreaded polygon shade look!!

Grab the YAS *.fsc model for more detail.
Ken