Ram ?

What will adding more ram do for me?

It can help speed up your PC, as ram is much quicker than a hard drive when processing information, the less ram you have the more the OS uses virtual ram, which is the hard drive.

Is it as simples as replacing the Ram boards/cards with bigger ones?

Yes

Do I need to backup the computer to add/change ram?

Always advisable to backup your PC before adding new hardware, but changing ram should not affect data stored on hard drive.

I have a 2002? Toshiba Satellite how much ram will it accept?

Use the Crucial memory tool to asses what ram you need and how much you can add.

Also check Toshiba's site for any info diagrams on how to change the ram.