My gf has a dell laptop that keeps overheating to the point that it shuts off and is too hot to touch. I was going to go inside of it and see if it was dust buildup inside of the fan unit. If it wasn't, I was going to try and replace the heatsink/fan.
Question I have is, if i just go inside and clean out the fan (assuming I'd have to pull up the processor to do that, would i have to clean and reapply the paste if I am not taking the heat sink off?
Most laptops (including Dell) have a fan/heatsink which is a single unit (very few - no Dells I know of) will allow you to remove the fan only. This guide will show you what is involved http://www.insidemylaptop.com/replace-cooling-fan-dell-...
I don't know if this is your gf's model but is representitive of the Dells I've encountered (only 2). You would need thermal compound before replacing the fan.
The guide you linked shows taking out the fan without the heatsink. I actually went ahead and just took it together myself due to not being able to find any helpful resources online. I took just the fan out and cleaned it, will monitor the temperature the next few days to see what happens.
The website you linked is a helpful resource, will bookmark for later issues.