As a beginner, you did very well so far, but you will definitely need to read up the basics of managing a Ubuntu system. As you said, it is totally different to XP.
My best advice for the moment is to use a headset until you have sorted out the internal microphone issues.
Alsa Upgrade Script thread? Yes, it's a rather lengthy thread but I am afraid you will need to read the first post from cover to cover ;)
It basically involves downloading the AlsaUpgrade script and executing it. Extract the file to your home folder, open a terminal and make it executable:
chmod +x name-of-the-extracted-file
Then run it:
If you do run into problems, post your questions to that thread since it is more likely to be heard by people who can answer your questions.
Distributions such as Ubuntu provide Linux software in so-called packages. Use Synaptic package manager to install/remove/update software:
System | Administration | Synaptic Package Manager