Did you checked the hall sender on the distributor or the crank position sensor? I've never had to replace an ECM on a VW before so I doubt that's the problem. I think you probably have a bad crank position sensor.
Yes it will, it's the most common thing that will cause a no spark condition. If you are getting a pulse on the middle wire at the distributor then I would suspect a bad crank sensor.
There's not a good way to test the crank sensor unfortunately that I've seen, do you have a scan tool to check for codes? Does the tachometer move when you crank the engine?