Tvheadend install problem : debian packages are mising

hello everybody,

I'm trying to install TVHeadend to use my NAS as a PVR (TVHeadend server on my NAS / client as add-on with xbmc)

I follow the official installation tutorial for ubuntu/debian : https://www.lonelycoder.com/redmine/pro ... i/Building

I have some issues trying building/packaging it because of some missing packaes/library on my readynas ultra 2.

I'm pretty new to linux, but i've understand that the readynas is on ETCH debian release, which means 4.0, an old version

When i try to do this :

sudo apt-get install libavahi-client-dev

and

apt-get install libcurl4-gnutls-dev

i have the following error messages :

Couldn't find package libavahi-client-dev

E: Couldn't find package libcurl4-gnutls-dev

Do I have to edit my /etc/apt/sources.list ?
i've found one the pakage here : http://archive.debian.net/fr/etch/libavahi-client-dev
But can I install it without risk ? because it strange that apt-get can't find it...

Well, if anyone can help me :))
Thanks !

Will