Depends really just exactly what they are wanting you to do. If they are testing how well you can integrate services you should be looking at something like an LDAP server so you can easily combine your samba and ftp. Then again, if it's just a filesharing system, and if you are allowed to use 3rd party software then if I were you I would just grab FreeNAS - http://www.freenas.org/
- and have one of the best free file sharing systems around thats supports anything.
FreeNAS might be considered cheating as you'd have it all done in 10 minutes :-)