Surveying corporations

I have an idea for a software right now that I know for a fact can help middle managers in customer service centers in the big 5 canadian banks.

The problem is that I don't think I have anywhere near the experience to deal with the big 5 so I would just like to know if it has broader appeal.

So I had a few qs:

1-Do the principles from selling SMBs or individuals work (assuming you reach the decision maker)? Many people do not think so because of commitees and such.
2-For those that sell software to corporations, do the IT department sometime give you trouble? And do they sometime just take your idea and run with it?
3-At what size do companies usually start having a middle management layer?
4-At one of the companies I worked at selling conferences via the phone, they had two people just doing surveys prior to setting up new campaigns.They got the name of the DM (hopefully) and his title, they asked them what they needed, etc etc.

So is it a good approach to do surveys to get info on the corporate structure and who is who? Or would it be simpler to simply rely on the good faith of the Gatekeeper?

Thanks