If you need a program like MicroSoft Office you can use Open Office or Libre Office which comes preinstalled with most Linux Distributions. Linux Mint is the Most used Linux Distro and is based on Ubuntu which has the largest repository of free open source programs available. This is a great way to test and then use if you like or delete if you don't and try another option. You can also run Linux Mint Live from a USB stick instead of installing it to your Hard Drive. If you want it to look like Mac OS X you can then install the macbuntu package.

I would Suggest using Bootcamp to create another bootable partition and install Linux Mint (Cinnamon, Mate, KDE, XFCE). I prefer Linux Mint but you can try any distribution. If you find that you can not upgrade to Yosemite due to all of your installed Programs not being compatible or have to spend a lot of money to upgrade them I would suggest installing a Linux Distribution. OS X - Upgrade to Yosemite - Apple Support However, some Software Features will not work.

Hardware Requirement: MacBook (Late 2008 Aluminum, or Early 2009 or newer).Snow Leopard is the last OS X with Rosetta for older software but Mountain Lion has a longer life time left. If you go this route make sure you back everything up completely incase you need to revert. Yosemite will work, However, You are on Leopard not Snow Leopard so you have to purchase a valid Snow Leopard, Lion or Mountain Lion license in order to install Yosemite.

Upgrade office 2008 for mac