How are the roof and waist spoilers stuck onto a 'classic' 5 door Impreza?

Mine's a GL and I want to put the spoilers on (don't worry, I'm not doing the bonnet too ;)) but am wondering how is best to do it.

Obviously the waist spoiler is stuck to the tailgate, but is the roof spoiler actually stuck to the roof or the top of the tailgate?

How are they fixed - could my car be returned to standard without drill holes showing etc?

If they're both attached to the tailgate then would it be best to just buy a whole turbo/sport tailgate from the breakers instead of the spoiler? Grade A said £100+vat for both spoilers and the high brake light, how much is a tailgate with all of those already attatched likely to be? Colour is code 406 silver so hopefully pretty easy to come by.

Thanks in advance,

Ben