Secondly I need to be able to upgrade from Leopard to the latest operating system Maverick
The first step in Upgrading... is to Snow Leopard = OS X 10.6.x
It is Not available as a download... It is a Paid Upgrade.
Do this first...
Check that your Mac meets the System Requirements for Snow Leopard...
Snow Leopard Tech Specs
If so... Purchase a Snow Leopard Install Disc...
After the Successful Install, run Software Update to get the latest updates for Snow Leopard and iTunes.
Check here to see if your Mac is compatible...
If so... would recommend at least 4GB of RAM... if not 8 GB
It is important to get the Correct and Matching RAM
See Here > OWC RAM > http://www.macsales.com
The above site also has videos on how to Install RAM should you need it...
Also... Check here for compatibility of 3rd party Software you may be using... Also note that Rosetta is no longer supported in Mavericks, Mountain Lion and Lion.
Mac World Installing Mavericks.
It is both Prudent and Recommended to Backup Before any Major Update or Upgrade.