Program:
http://store.autodesk.com/DRHM/servlet/ ... =103837600
Unit Cost: $3,495.00 USD
Difficulty:
Immense.
The problem is its not a simple click and go venture. Simply creating (or even more simply, editing) a mesh requires some working knowledge of the software. Fortunatly there is a few books available, and two or three hundred tutorials at least available online, that can teach you these basics.
After that it gets easier mind you
The good news is, whilst you're saving for the program, and learning from books, you can spend your time gathering resources for the build. For example, are you going to make one basic B-17 pit, or several different versions?
Say, you had some experience with 3DS Max, and model making, you should still be able to turn outa vague lookalike within a couple of months or so.
Thats if you wish to make a proper B-17 pit. You always have the option of making a, dear I say it, Franken-Pit, which is made from bits already ingame. This way you could get a rough facsimilie of a Fort's pit. This is done with a lot of co-ordinate editing.