Well, being that you will be trying to fix a TV, chance are, if it's a newer TV, it has lead free solder. That 30W iron may have trouble with that solder.
The thing with a 60W iron, correct me if I am wrong, Is it gets too hot, and you could heat the pcb trace too much and raise it off the circuit board when trying to remove the solder paste. Probably not much trouble when soldering, as that is usually quick. But, again, if you get the 30W, and it's lead free solder, you may have trouble getting the solder to heat up and come off.