first question, why 8.04? That is really out of date. It will work, but is really out of date. Try 10.04 or 12.04 if anything. If they are hard on your system, then Lubuntu is a lot better in that regard (looks better too).
After that upgrade to 12.04 and install MATE/LXDE and you will be up to date.
what do you need to do with the programs?
There is no need to use AV as long as you are not a complete fool when you are using it (seeing as there is very little viruses to affect a linux system).
Really, there is nothing you need to add to a Ubuntu install to make it work. There are a few things that can be added if you so want, like other window managers, conky, and chrom(e/ium).. Anything else you want can be pulled from the software center.
Is there a reason why you can not just download the newest version? That would be a lot easier than upgrading.
Did you download and burn it yourself, or is it a purchased disk?
What that is saying is that there was an error in OpenOffice that was caused by a missing dependency.
Check your MD5 hash on your download and make sure it matches. If it does not, then you need to download it again until it does match.
Really, what you should be doing is using the most current LTS or release disk and installing from that. The upgrade process can be dodgy at best.