I would get it serviced elsewhere. Not that there is anything wrong with getting it done at a dealer, but there are plenty of specialised workshops who can do it for you cheaper probably too.

Shouldnt affect your warranty i had rear strut replaced even with having springs on it.

For Bonnet scoop consider www.ultrex.com.au

In regards to Brant they can/do go skitz, make sure its had all the recalls done.