The ICM's are hard to test. They can pass a test and fail on a vehicle.

However, more often than not...the vehicle will start but once it gets hot it'll loose spark.

Yes you should, but that isn't the best way to do it. Go ahead and pick up a spark checker next time you're at the auto parts store. They're cheap and are a reliable way to make sure you have no spark.

I've seen a lot of people chase problems for a long time based on false initial information.