I would just leave it the way it is still. Laptop always tend to run hot. Actually, people at work are saying that it's preferrable not to keep laptops running for 24 hours consistently. It's better to have it in hibernate or sleep mode should you do leave it on because of the heat issues with laptops. No matter how good they are, heat is always the enemy with these small form factors.
Oh, I should add: it's a pain to upgrade laptop CPUs. I tore my old laptop apart so I can salvage the parts. Wooo, the CPU was a pain to get to. I have to take apart layers and layers of crap including the massive heatsink/blower combo it has. There were tons of wires all over the place making access difficult. Thank goodness I'm never using that laptop again. It was a Compaq V2000 series laptop. Terrible build too. Those Turion CPUs just don't cut it.