Is there a particular reason you want turbo as opposed to supercharger? Any particular reason you prefer single turbo over twin turbo?
If you're lucky you can find a used system in the for sale/wanted forum for a good price. That's what I did.
For a complete kit + tune, you're looking at minimum $6,000. Not to mention things that you'll want to upgrade, like bigger tires and/or wheels, stall kit (auto), better clutch (manual), etc.
Also keep in mind that to go to the track in a convertible which will do 1/4 mile runs in less than 12.00s, you'll need a roll cage or hard top, if the track is enforcing their safety requirements.