dont buy front cips from ebay.. i wouldn't trust it
i don't understand what you mean by 240 to silvia conversion..
yes there's the sr20det swap.. are you talking about s13 front end or s15 front end??
you need, oem fenders, hood, lights, bracket, and a front bumber. bumper support will be lost. i would recommend going to a shop to do this.
no you do not have to ship parts from japan after you have done the sr20det swap. there are plenty of shops in the country that have sr20 parts in stock.
www.phase2motortrend.com is one of the greatest 240sx/sr20 shops i know. they also carry front clips and a lot of info abou the sr20 swaps
there are no such thing as dumb questions. i believe that forums were made so that knowledge maybe passed onto others =)