BOAC
I think you are going down the road I travelled. Previously an owner of a Psion 3c, for which I wrote a few application using the built in EPOC compiler. Have moved on to Pocket PC and attempting to do the same.
I found trying to go down the .Net route very confusing and potentially very expensive. I ended up with
NSBasic. Does not come with much documentation, but it is fairly easy to pick up.
T'bug