The first thing you should do is to have server-side q2a "services" exposed by http.
That is you should have q2a APIs exposed (as twitter, facebook, and so on do...)
I've seen there is a plugin ( https://github.com/NoahY/q2a-xml-rpc ) that offers an xml-rpc implementation. It's not a rest api (the standard now) but you could give it a try. If it works, it could be ok.
About the client side implementation you have 2 choices :
1) write a native app : I'm not a "windows man", I think you should use c# or c++ as a language
2) write a portable app : you could use a platform like Apache Cordova (for example; see http://cordova.apache.org/ ) and develop using "more common" languages such as html, javascript and css)
The advantage of the second choice it's that the app is portable also on iOS, Android, etc etc
But it's not native, so you could not have the same user experience and performance of a native app.
I think that for simple apps Apache Cordova (or similar frameworks) should be ok.
About the cost, you should ask for an estimate explaining exactly your requirements.
There are a lot of guys offering great q2a development services 
