My two cents:

Creating a map is fairly straightforward. If you've played a game like Sim City, you shouldn't have too much trouble building out a simple map: it's mostly a matter of dragging and dropping pre-existing map pieces into your scene.

Writing dialogue is also pretty simple. There's a big difference between writing a short story and writing game dialogue, due to branching trees and conditional content and such, but it isn't too hard to get the hang of it.

And, finally, designing basic combat isn't too tough as long as you stick to the pre-built enemies and don't try to do anything too elaborate. You can drag-and-drop enemies into the map, and the default AI does a decent job at fighting.

So, you can probably get a rough version of a game up and running even without previous experience. But, turning that into something that feels more polished or involved will be more challenging. Some of the more difficult things to do are:
* Adding dynamic lighting to your map
* Creating cut-scenes
* Making anything custom (map props, weapons, spells, etc.)
* Elaborate fight sequences

A good first step would be checking out the tutorials[shadowrun-returns.wikispaces.com] that HBS put together. This will take a few hours, and should give you a good idea of how tough it'll be for you (and, more importantly, whether it's fun or not!).

Specifically regarding turning a short story into something interactive, I highly recommend checking out HBS's guide to branched dialogue[shadowrun-returns.wikispaces.com], which gives a good overview of how an interactive game will differ from prose.

Good luck!