Hello, my name is Dan.
I will do my best to help you, the only stupid question is the unasked one.
Your Mac can run Mountain Lion 10.8.x with some additions.
Ram being the most important.
It can take 6GB and that is only $140. It will make your Mac seem like new.
They also have instructions to do the job, all you need do is follow what it tells you.
Since you have Leopard 10.5 getting Lion or Mountain Lion is a little more difficult, Apple does not sell disks to install from and they want an arm for a USB drive with the OS installer.
It is all done online from the APp store which your OS X does not have.
There are ways to get Mountain Lion installed without first installing Snow Leopard 10.6.
Before you do any upgrading make sure you have a good full backup of your Mac. If something goes wrong you may have no data left.
That said, if you know someone that you are comfortable with tech wise then I suggest enlisting them. They are around and finding them is easy. Just ask at church or your friends or even at your local Apple store. They can point you to a user group in your area.
This explains how to get OS X 10.8 without having to buy 10.6 first (expensive now as Apple no longer sells it).
Please read it through before making up your mind. You may be able to get away with only the RAM to keep up, it will make a big difference.
Does that help?