Sources.list Question

[Fred White <subscribe@cakafete.com>]

Hello List,

I am learning to help myself installing and updates some minor programs 
on my dedicated server and need to ask a couple of questions.
I need to upgrade Opendkim version 2.0.1 but squeeze repository remains 
with 2.0.1 since I started have to add opendkim to my server and this 
version seem never to be upgraded. However, 2.6.8 is in Debian backports 
repository and since I do not want to update any other areas of my 
server seeing the warning of incompatibilities that might be introduced 
by the packages using the backports could cause my system to become 
unsupportable I want to be carefull.
Could I just rename my present sources.list and then just create a new 
sources.list with just the one line "deb 
http://ftp.at.debian.org/debian-backports/ squeeze-backports main"
then #apt-get update
then #apt-get install opendkim
Would this be right or should I be using dpkg.

Please advice any input would be much appreciated

Thanks

Fred