Richard,
Do a "Search" for PDA GPS and look through the archives. We have been discussing the topic to death here in the last couple of months. This might get you some base information to which you can then ask more pointed questions.
There are several options, and would sure hate to miss some of them for you. Unfortunately, many of the discussions ended up being off the original topic line, so the search should display those with PDA GPS in the body of the post.
