I am expecting that you've got full specification for data format of the exported data (complete with expected responses, etc.). The same goes for your web-service (hopefully no discrepancies between official docu and the actual implementation, as is sometimes the case).
Speaking of project implementation, I've got a can-do attitude, excellent C# skills, fluent English and am currently not working on any other projects so you can be assured I would be fully focused.
To back my claims, I'm willing to write off the costs of prototype development - effectively taking twenty-percent off my initial bid.
Looking forward to hearing from you,
J.D.