If ou are just getting started here are some suggestion:
1. get the book Mastering XPages from IBM Press as well as the companion on XPages Extension Library
2. I would strongly recommend that you take the XPages Introduction course from TLCC (it is free) and consider the other XPages courses - I don't receive any consideration from TLCC for this commercial :-)
3. Check out the various videos on NotesIn9
4. Start by developing a fairly simple application, then tackle the one everyone wants done.
5. You will need to plan your application much more in XPages than in traditional N/D.
As you said the move to XPages from traditional N/D can be a pretty daunting task. There are lots of resources out there but getting a specific answer can sometimes be difficult. Some parts of my development I have started over several times because I found I painted myself into a corner or found a much better way to accomplish the job. This is much easier to do with a simple application. Plus I have found ways to do some things in XPages that I have wished I could have done in N/D, also some things that are a snap in N/D are not that easy in XPages.
Be prepared for a fair level of frustration, but then one day you will say - hey this is pretty neat!