Well, assuming you have net and have the right URLs in place, one way to get maps on the thing is to (1) zoom all the way out to level 15, (2) choose "Maps > Auto-Download", and drag-scroll around the screen to download map tiles for the entire world at the highest zoom level. Now you will always see something on the screen no matter where you are. Now turn off auto-download, zoom in several steps on the part of the world you're interested in, and turn auto-download back on to get maps at that zoom level. Repeat the process for each zoom level and region you care about. For instance, I have maps at zoom levels 15 and 13 of most of the world, at 10 of North America, at 8 of DC, New York City, and New England, and so on down to zoom level 2 of the town I live in, the area around where I work, and so on.

The first time I installed Maemo Mapper I did all this by looking up longitudes and latitudes on one of the Google Maps tutorial sites (http://maptracer.50webs.com/tracer.htm wasn't it, but it has the same functionality) and entering them by hand in the download-map dialogue in Maemo Mapper, but the last time I decided it was a lot easier just to turn on auto-download and scroll around on the map to do it visually.

Routes and tracks are essentially the same thing, stored in the same format, except that the assumption is that a track is a record of where you've been, while a track is a record of where you want to go. If you don't have a GPS, you probably won't use tracks at all. (Another difference is that a route, being intended as directions, might have human-readable directions like "go 50 feet, then bear left onto East Cowpath Lane" embedded in it. However, the file format for routes and tracks is the same.)

There are two ways of getting a route onto the N770. You can use the author's "GPX Driving Directions" page at http://gnuite.com:8080/cgi-bin/gpx.cgi , or you can do the same thing from within Maemo Mapper by choosing "Route > Download...". In either case, though, the form requires valid and explicit addresses (or else latitude/longitude pairs) for the Origin and Destination fields -- you unfortunately can't use a partial address like a city and state. And the address parsing seems to be stricter than Google's own address parsing.

However you produce a GPX route file, it doesn't really matter where you save it to. I save mine to a sibling of my maps directory called "routes", but you can save them in your Documents folder (which corresponds to ~/MyDocs), at the top level of your MMC card, or wherever you like.

Hope that's a useful start!