When you get the hang of assembling the links, it goes pretty fast. Count on at least 3 hours to assemble two sets of tracks.
There are quite a few "spares". I have not counted them but it looks like you can get a "free" set for every 5 sets you buy.
When they are assembled, you can spray the tracks an appropriate color...."old rust" with some washes of "new rust", or the blueish black of cast manganese steel then sand the high spots to leave shiny bare metal where the track "polishes" itself from use.