C# wrapper for Google/Yahoo API's

We are looking to have a C# DLL component created which will provide us a single API to integrate our system with the Google, Yahoo and Microsoft keyword Ad systems. All three search engines have published and documented API's that provide the ability to create keyword Ad campaigns on their engines, and retreive the performance metrics. This wrapper component will implement a single set of methods, which we can then use to place our keyword Ads on any of the sites. We want the design/architecture of this component to be extensible, in the sense that we can add additional keyword Driven sites that have an API. The component should have a clearly defined process of implementing the specific methods. I have attached a definition of the exact set of methods we would like to be implemented in the API, along with the method signatures, and a description/purpose of each method. We are open to discussion as to the specific details of the API, this document is meant to convey the scope of what we would like implemented. Each search engine has a "test" environment where this development work can be done against. We already have our API credentials, so we can provide those for the development testing. We strongly would like someone who has knowledge/ worked with these API's before...as that will make this project MUCH easier...but if you don't have experience with them, you are still free to bid, just don't include costs for getting ramped up on the API's...as we are looking for developers who already have working knowledge of them.