If your Laptops fan is still operating (but sounds faster and louder), then before you open the laptop a good tip first is to buy a can of compressed air.
Remove the battery, remove any back covers you can without removing any internal components, stand the laptop on it side in the open position, use the compressed air blowing through the keyboard (do this outside) you will be amazed at how much comes out.
This is worth a try before going through the process of stripping it down.
Rich