A friend of mine has been using a canon 35mm film camera for some time and I have convinced him that the time is right to go for a canon dSLR. He'll be buying a second hand 300D. He has a couple of EF lenses which will do fine. He also has a flashgun, he thinks it's the 300 EZ. He says he's seen someone else use the same flashgun with a dSLR. Is it compatible with the 300D or should I convince him to buy something like the 420 EX?