Need Macbook Help (keyboard problems and reinstall questions)

Ok so got a Macbook off a friend new to the platform and had some questions/problems.

randomly keys will not work or will type wildly i.e I press w and get a whole string of 7's across the screen or several letter of the alphabet decide not to work. I'm running 10.5.8 Snowleopard I believe I was wondering if this sounds more like a driver issue (maybe he installed a wrong driver or software conflict) I personally think it's a hardware issue since a usb keybaord seems to work fine when plugged in it's just the laptop keyboard that acts up and misstypes stuff or types on it's own at random.

Also if it is a hardware issue how to i format and re-install the only install dvd I have is a 10.6 version of snow leopard will this work for me or do I have to hunt down a 10.5.8 copy and if so where?

I personally believe it's a hardware issue with the keyboard unit which from what I can tell can easily be replaced I just wanted some other oppinions before ordering a keyboard. and the administrator acct the password I have for it isn't working so also looking to do a fresh install even if it's just a hardware issue to set it back to default or is there a way to do this without wiping and installing without root permissions?

Thanks in advance sorry if questions sound dumb but new to the platform usually run windows 7 and ubuntu

 

Ok I went and bought dual layer dvd's to make an installation dvd for this tonight but all it keeps doing is spitting the dvd's out over and over I moved the .dmg file to a external hard drive to try and just access it from there but not being familiar with os x I'm not having much luck with doing anything since I dont think the drive is just a dvd player / cd burner drive.... I've read elsewhere if it's unable to burn the media it will likely not be able to play it but I finalized the disc's when burning them so they should play anywhere a regular dvd should play