Hi Bruno,
You can go the way most people are going these days and build a McWire Cartbot
to repstrap all parts for the darwin.
It's easiest to just buy everything from ian (bitsfrombytes) but maybe less fun
So I'd prefere buy only the extruder (because it's really hard to make an extruder yourself) and then print the parts you need with your just homemade RepStrap
'sid