What these guys ^^^ have said, + check for movement and play on the rear hubs as well as checking for any bent arms, however more that likely it will just be geo. adjustments.
This is what you need for on car work.
http://www.ciponline.co.uk/vehicle-service-c2917/braking-c2962/on-vehicle-brake-flaring-tool-p35505/s37156?utm_source=google&utm_medium=cpc&utm_term=sealey-on-vehicle-brake-flaring-tool-14143&utm_campaign=product%2Blisting%2Bads
Use the proper fitting tools in the first place.
Now you will have to try a slightly larger size, give it a slight tap with a hammer so that it is good tight fit and bobs your uncle.
I have a 350z HR (07-08) STILLEN Generation 3 Ultra Long Tube Dual Intake Kit coming off a car next week.
Been on the car for 8000 miles.
£300.00 sounds about right.
Alex.
Don't know, however imho I think that the side skirts are hideous.
I am sure that some of the body kit experts will be along shortly to answer your questions.