Debian Installation :: Installing The Squeeze Graphical Desktop?

I am trying to install Squeeze (Debian 6.0.2), KDE environment, desktop PC, older 32-bit single CPU, 40 GB hard drive wholedisk, 2 GB RAM). I am trying to install an encrypted hard drive (takeover installation using entire hard drive).

Each time I try this I seem to run into different problems, and to date I have not succeeded in obtaining graphical installation. My most recent previous thread on my problems is at

viewtopic.php?f=17&t=67113

It contains video controller hardware information. (In that thread I mentioned a desktop and a laptop; I am currently trying to install Squeeze on the desktop PC, not the laptop!)

It seems I will need to request using apt in the shell the Squeeze package firmware-linux-nonfree. I am not familiar with configuring apt from the command line. Can anyone just tell me what I need? (I have many other things I am trying to learn today, so RTFM would not be helpful in this instance.) I am hoping apt will be autoconfigured well enough to get the deb if I simply give the command. Would it be

apt-get install firmware-linux-nonfree

I want to ensure before trying to get apt to install debs over the internet that the key-signing and package verification is working. I hope that all is done automatically by the installer, but does anyone know with certainty? I stress that (as I understand things) checking the GPG signature of a signed deb is different from and complementary with checking the integrity hash; both verifications are crucially important. The reason I ask is that at least under oldstable (Lenny) there was a separate debsig package, which seems to imply that apt does not automatically acquire the ability to check the GPG signature of signed debs.

Someone said that in addition to non-free drivers I might need to obtain firmware. I have never been able to do this successfully, probably because hardware sites assume Windows users and I don't use Windows at all.