[misnomer]

I am a bit confused on this whole fan shroud thing. Most folks getting electric fans do away with the shroud entirely and place the fan right up to the radiator. These fans will typically have a shroud of sorts build around them, but they will be very close to the radiator. The point of the shroud is to force air to follow that path, allowing the crank fan to suck air through the radiator without having to be right up next to it.

1) Missing a tiny bit of radiator from the shroud/new fan shouldn't hurt too badly.

2) You want it to be pretty snug with the radiator. Air that is pulled in from around the fan shroud is air that doesn't cool your radiator. If the radiator is melting the plastic of your fan shroud, you've got some major cooling issues :P

3) Get a thermostat. If it's on all the time, your engine will run cooler (possibly too cool, it's built to run at 210-220 degrees), and the temperature will vary a lot. That's bad. Temporarily, it will work running it all the time, but fan thermostats aren't too spendy.