The 9800 series had 2 kinds, one with the r350 chipset and one with the r360 chipset. The ones with the r350 didnt have any temperature monitoring. Here's a way to tell if its getting too hot, play a game or 3dmark, if there's artifacts then its too hot. If not then dont worry about it and dont bother taking the fan off, it just increases the chance you'll wreck it (I did it succesfully on my old one to put AS5 on it).
I really didnt find my 9800 that noisy, but maybe if you are coming from a non fanned card you notice the difference, I can guarantee you my computer is louder. Just make sure that theres no wires in the fan, that can be annoying as it will make a lot of ticking noises.