Many thanks to all who responded. I received some great ideas on how to improve on what's available, a couple of good references to papers, and some references to existing code.
I am still working on the foundation which consists of an event-driven message bus which loads modules that then either subscribe to or trigger particular events. It's written in C# and is running on mono, so is effectively a multi-platform binary.
The modular architecture allows me not only to bite off a bit at a time, but to easily support hosts with varying capabilities.
I've completed a rotator module which is successfully tracking satellites with my GS232B. (Woohoo - that's exciting!).
I've also written a module which uses Predict as a data source, but that's limiting me to having network access to a linux box running the predict server.
The next two items on my to-do list are a .NET native prediction library and simple FM tuning.
I'm considering using some code from Michael F. Henry who wrote a SxGP4 library in C# (http://www.zeptomoby.com/satellites/ - if you're not already familiar with it). Otherwise, there's a C implementation at http://www.sat.dundee.ac.uk/~psc/sgp4.html which most likely could be adapted to C# fairly easily.
Tony Monteiro's code is also a great start for modeling satellite data such that it's useful for use in tuning to the different modes available.
Thanks again.. I'll let you all know how I progress!
Scott NW2S