I've got similar model from EB range, which originally came with i3 370M. A couple of years back I replaced it with i5 480M, and now I'm running i7 640M, all without problems, cooling seems to cope rather well with additional power, and according to notebook-check.com the i7 640M is about 50% faster than the i3 370M, so the upgrade is worth it. I actually type it on my Vaio and there's EA app in the background running some updating and the task manager shows 100% CPU energy all the time, and CPU temp is 71-74 degrees Celsius, so not too bad given it runs on 3,2 GHz on Turbo continuosly. Keep in mind, however, that I try to replace thermal paste every year and I clean the fan regularly, and I use the Thermaltake cooling pad (my exact model is called Massive 17, I think). You totally can replace the CPU and it's rather simple, just take out the bottom plate and disassemble the fan with the radiator, then the CPU will be right there. Hope that helps.