2) 16k miles is GREAT however that price isnt. for 19k you can get a used 06/07... try to chew down the price. you should look for any modifications... the more stock it is, the better.
3) well, i've had 3 hondas previous to the wrx and i've found them to pretty much be the same. of course regular oil changes are a must... and for the wrx there are points that we have to have "major inspections" (30k miles... 45k miles... 60k miles... etc etc) which will probably cost a bit