What temperatures are you getting? Use HWmonitor. Get the free version. Post up a screenshot.
Heat is a common problem with laptops. It has little space for the heat to expand, unlike desktops. The only way the heat has to go is out the side vents. So that is why all the hot air makes the bottom hot.
Cooling pads are meant to do both. Cool the underside of the laptop, and protect your lap. There are different types, though. There are ones that are meant to be used on a desk, or just in your lap.
I personally use this: Newegg.com - Targus Lap Chill Mat Model AWE55US
It's whisper quiet, and keeps my laptop at a constant 40C.
For dust removal, all you need to do is spray some canned air into the side vents. This is the most crucial place for heat dissipation. Opening the laptop is very hard to do. There are several layers you need to open. Unless you are a professional at it, I would not recommend it.