目標が単に通常のデスクトップアプリケーションにマルチタッチを追加することである場合は、Windows7の.NET4.0を実際に検討する必要があります。そうすることで、既存のアプリケーションから始めて、便利なマルチタッチ機能を追加することができます。
If you do go to Surface, the primary changes you'd see in your code if doing a direct port would be changing all of the built-in input controls to the Surface versions (i.e. Button to s:SurfaceButton). This needs to be done to support Surface's Contact inputs, which don't activate things like Button.Click on the standard controls.
There are a few more important concerns with Surface applications that you can't really get a feel for just using the emulator on your desktop. First is the multi-user experience, including not only the huge number of simultaneous touches it supports, but also the multi-directional orientation of the UI. Since the Surface is a horizontal screen users can come at the application from any side and the application itself can also be flipped vertically depending on which direction the user starts the application from. This can require a lot of thought around how the features of a desktop app need to be reworked. Surface also has a fixed resolution of 1024x768 which can also make for awkward transitions from dynamically sized desktop apps made for large screens.