I can't answer your questions about the radiator, but a sucking fan is on the engine side of the radiator. You'll probably want to go for this because 1. You have more room for it and 2. based on the ones I've seen, the sucking fans draw a bit more air through the radiator.
I've recently replaced my fan with a Revotec one from Demon Tweeks. It came with the fan and a plug that was completely incompatible with the one for the Polo fan switch. I just cut it off and joined the wires with the ones from my existing fan switch. A 5 minute job if that...