Laptops do tend to run warmer but that definitely does seem too high. Graphics can be particularly susceptible to heat in some models and the symptoms you're describing sound like artifacting to me, so yeah I think this is all heat related. Check out your fan vents first of all and remove any dust, compressed air works well for this. If it's still running hot it's possible that a fan has died or a the heat sink for your cpu may need some new thermal paste (or possibly even replacement but that pretty unlikely). I don't have time to dig for a service manual right now but if you use Google you can probably find one easily enough, or some ad hoc instructions for getting at the cpu. Usually it's just a few screws on the bottom and then you just lift up the keyboard and disconnect it.