Total Meltdown - OS X features not working properly

Hey everyone, this is my first post and I 'm desperate for some advice! My ibook seems to be disintegrating one feature at a time...

Ok, firstly a week ago my dock disappeared, nowhere to be found! cannot drag anything anywhere, do no functions such as shut down restart etc. my using the top menu bar, only with ctrl+shut down button etc etc.

And NOW all my sounds are off, a while ago my microphone stopped working and now i can't even hear a thing from the speakers, so no sound whatsoever!

As you can probably deduce from my lingo, i'm hardly an expert when it comes to technology, main reason to have an apple! I'm just wondering can all of this be fixed? Or just buy a new one, in all fairness mine's 4 yo old already..
Could it be a virus? Just moved to Moscow and been using wireless.. really worried abt getting my ibook serviced here, anyone have any ideas how much repairing these faults will cost?

Thank you so much in advance for reading my plea for help!

Pop in your install cd (the one that says "hardware test") press D when starting up and see what that brings you.
Post the results here.

Based on what I read here, it could be the logicboard, but it's better to be safe than sorry.

Good luck