download the istat widget, found
here. Feeling hot is too subjective, but once you have hard numbers you can check back here and see if their inline with others. Also you'll be more apt to get support from apple if you can show that it is indeed running too hot.
As for the performance, that really doesn't sound like a computer problem but rather a internet bandwidth problem. What are you using for an ISP, dial up, dsl, cable? Is there a way you can see if another computer works fine?
Also check the network utility (found in applications->Utiltiies) that can show you the speed to which your computer is attached to the cable/dsl gateway. It will not (I don't believe) will show you the speed of your connection on the internet but at least it will highlight any possible bottlenecks between your computer and the the cable/dsl modem (provided you have cable or dsl)