M_Boats: gps

Am looking for recommendations for a gps setup to use on my 17 for coastal cruising. Will a handheld suffice? Would I need one that will download charts? How will I know where I am when I am far enough off shore such that no physical markings are visible on the gps screen? Does the gps give lat/long readings which I then need to look up on a chart? Any advice will be appreciated. Tom B, M17 #258