I have a ceiling fan/single light combo, and the pull string to switch on the light is stuck... How do I dismantle the light fixture part to get at the string?. Will I need to replace anything inside?

Yes, the pullchain. It's really easy.

Ceiling fan pull chain replacement and repair - Ceiling Fans N More (http://www.ceiling-fans-n-more.com/ceiling-fan-pullchain-replacement-and-repair.php)