The following site contains a lot of tutorials regarding DNS-320 and FunPlug :
http://wolf-u.li/nas/tutorials/ffp/ it's in german, but you can always use Google Translate.
This is the complete step-by-step FunPlug installation (again, in german but you can translate it) :
http://wolf-u.li/4523/hdd-installation-des-fun_plug-auf-nas-geraeten/
P.S. You should use Wolf_Uli's repository, it usually has the latest versions of packages.
P.S.2 there's another tutorial in english, it's for an older version of FunPlug (0.5) and for DNS323 which is similar, might be usefull though
http://nas-tweaks.net/40/installation-of-the-fonz-funplug-0-5-for-ch3snas-ch3mnas-dns-323-and-many-more/