We got the parts for this Extruder already with the MiniMendel parts.

http://reprap.org/wiki/Mendel_extruder

So we will use this one.

I got a Ø0.6mm nozzle.

The heat barrier will be made of epoxy.

I decided to use
http://aka47.adsl24.co.uk/serendipity/index.php?/pages/min644p.html
and
http://reprap.org/wiki/All_In_One_Electronics
which will reduce the costs enormous.

Links, because FTP is incooperative:
http://reprap.org/mediawiki/images/4/4d/Mendel_Motherboard_PCB_Copper.pdf
http://aka47.adsl24.co.uk/serendipity/uploads/m644p/CpMin644p.pdf