Eddie already gave some advantages of mechanical desktop and Inventor over AutoCAD, but it go's further..
For example, Mdt (Mechanical) is entirely parametric which means that you can change your 3D-model in a split second.
Say you subtracted the pickup-cavity from the body, but the dimensions of the cavity are not correct. In AutoCAD here is where the story ends (a wrong 3D-model) (exept you put back some material (uninon) and then re-substract the correct cavity of the body blah-blah-blah)
But in Mdt or Inventor this is much much more easier. You only have to change the sketch (in this case the pu-cavity) and resolve your part and done is that !!
secondly, the 3D-module of Mdt is much more easier to work with and gives more opportunities than AutoCAD. I don't know about the 2002 version but in comparisan with AutoCAD 2000 the advantages are great.
Thirdly, Mdt has the surface modeling mode for the more complex 3D modeling. (AutoCAD 2000 didn't have this module or it was very limiting)
But then again, I'm very impressed of the fact that you drawed the body entirely in AutoCAD !!
For my guitar project I started last year and finished a few months ago, ( http://www.ghesqij-guitarsite.tk/
) I also drawed the entire axe -which I was going to make- in Mechanical Desktop. This way I already had a virtual prototype before the actual guitar was build.
The renderings can be seen by clicking this link: http://users.pandora.be/marnix.ghesquiere/specpict.html
All the images you see on this page are drawn and rendered in Mechanical desktop.
And then,.. Inventor. The latest evolution of Autodesk. In my eyes you can draw a 3D model in-no-time with this program. Much much faster than Mechanical desktop. The drawing style is similar to that used in ProEngineer (Pro E).
I don't know if Inventor has the surface modeling module (Eddie?).
I'm also not sure whether inventor has a rendering module the way Mdt has. -> But then again: you can export the part and render it in 3D MAX...