The springs are different ratings, check out the durango website for a spring chart. Light blue/dark blue is a fairly popular combination (apparently). So no, you don't need to match them.......
edit:- spring chart.
http://www.petitrc.com/setup/durango...ringChart.html
The ride height is likely as you have no running gear in it.
My 2wd is sans electrics at the mo, and that looks like its on stilts too.
If you have a look round on the Petit website (or durango for that matter) and get a more up to date/new set up sheet it should give you a better handle on where to start.
Get a half way decent charger, cheap rubbish will possibly just destroy your lipos, and anything within 20 m as well.
Look at spending £30-40 on an all in one as a minimum. LX41B is what i had (£40), upgraded to a UAC-50 (£50) when i sold my old car as an RTR (included the charger).