>... I don't know what level of detail is included in the unit.
The CX series come with a routable basemap, which show major features, roads, and highways. "better than nothing:
Basemap info at:
http://www.garmin.com/include/basemaps/americas_recreational.html
>Will I need to buy Mapsource Metroguide ($85)/Topo map (for hiking only?) ($80),
Up to you. Used copies of MetroGuide go for about 1/2 price on ebay, and are unlocked. And see below for a neat autorouting hack.
>USB adapter ($??),
Some come with. My venture cx did not; I already had a cable.
>uSD card(s),
Some come with, but are so small as to be a joke (64mb). I just tgot a 512mb at frys for $20, no sale or rebate.
>cigarette lighter adapter ($25),
dunno, but battery life is very long on the cx models. Might not need one.
> does the unit itself have all I would need for backroads exploration,
Depends on what you need.
The MetroGude stuff is find and shows county roads, aome dirt roads, etc.
You could get lost then get home again using just about any gps out there, including teh minimalist ones.
> restaurant/gas station finding, ...?
the Points of Interest stuff (which is what garmin calls it) comes with the maps, or in a seperate but near-useless database. I'd snag a previous-generation MetroGuide used off ebay and use that. Or ask for a current copy new for xmas.
You *could* buy the more $$$ CN/CS but they are irritatingly locked, and the MetroGuide *will* autoroute in the GPSr if you use sendmap instead of mapsource to upload them. There is something of a hit to indexing (finding arbitrary addresses) but I don't mind that.
>Are pre-programmed uSD cards something you can create yourself with CD-ROM and blank uSD or is
Normal retail microSD/transflash. Roll your own from the CDs. Or get crazy and make or hack your own mapsets. (much time and understanding wife required for the latter).