You will need:

• Time: not weeks but months and years
• Money: more than you might expect
• Access to sophisticated production equipment
• The ability to manipulate Gerber files
• The patience to order 100's of different components (some of them will invariably be 'on allocation' or newer-spec)
• The skill to debug multilayer-layer PCBs, and to devise automated test-programs
• The sang-froid to embark on a project of this scale
• The nous to identify partners who will support the project from beginning to end
• The experience necessary to manage a project of this complexity
  
• The commitment to see it through
• The sense of humour to throw it all away when it doesn't work [expletive deleted]

In short, it is neither easy, cheap nor quick to build; you'd be ill-advised to contemplate this for quantities below 1,000.