Yes coilovers are great. Currently have Tein Super Streets without the uppermounts. Theyre great and are adjustable both height and damping.
Your better off gettin the coilovers off a trader on Ozhonda, it would be about 1400 without uppermount, or 1700 with uppermounts. (rough figures). I got mine off a trader form here and many other Euro owners have as well.
If u got it from a shop, id reckon it would be a little more dearer than off a trader from OzHonda.
Oh dont forget that when u lower ur car, your gonna get neg camber. Depending on how low u go, will depend how much neg camber u get. So u may need a rear camber kit. Recommended one is Ingalls. Yeah i ve got one too, does the job nicely to fix -3.4camber.

As for installation of them, i wouldnt know a good shop as im not from Sydney, but the Sydney Euro owners would know of a few.