to get an idea of the price of the body kit have a look on pumaspeed's web site, best part of 2 grand complete ( plus fitting )

any tuning to the st170 will require a good aftermarket ecu and either itb's or a turbo, probably another couple of thousand

think it might be better starting with a st170 instead of converting yours either way it's more expense, forget pockets you need a big pot

If you would like to visit, look at my cars and throw some ideas around you are very welcome to do so