The best place to start is here:
http://www.nhtsa.dot.gov/cars/rules/import/
Under registered importers you have a list of shops in your area. They are bonded and authorized by DOT/EPA. The customs broker is up to you or you can work with someone they know locally. Broker will charge about $500 for the docs plus any applicable duty.
To get a true idea how much it will cost, you will have to narrow it down to the exact year car you are looking at so you can price the parts accordingly.
Now, if you find a car and want to close the deal ASAP because it's the buy of a lifetime, a savey broker can direct you.
1. TIB (Temporary Import Bond) will bring it in the US, but only for 6 months, then you have to export or destroy the product. Allows you time to figure out what you want to do with the car (keep or sell overseas). After the 6 month window you can satisfy the export requirement and keep the car here by entering it into a foreign trade zone or bonded warehouse - you will not have use of the car, but it will be physically here. Both are not part of the Customs Territory of the U.S.
2. You can also bring it in under a Carnet. Not designed for this, but will allow you to bring it in. The Carnet is like a passport for merchandise that allows it to move from country to country with no formal entry requirements. Mostly used on prof equip traveling with a person (TV film crews) and cars brought in for a race series, like Formula 1. A long time ago Lambo did something like the IROC series, I personally imported all those cars under a Carnet.
1 and 2 are not cheap and are only a last resort for a buy of a lifetime. The only proper way (and what I suggest) is locate a car FIRST.. then contact a conversion shop near you and get a customs broker.
Got your PM .. wish you were coming Sat/Sun because we are doing Moroso today and Italafest Concours Sunday...