What to expect if I import an amp and preamp from a Japan seller via US eBay

I can’t afford the cost of the amp and preamp I’d like to buy.  I’ve discovered I can pay just less than half what I’d pay at a dealer in the US.  But I haven’ t done this before.  I’m aware that I won’t have a guarantee and that I’ll need a step down transformer.    I willing to take the risk of no guarantee.  But I don’t know what to expect when my box hits CUSTOMS.  What can I expect?  What are my responsibilities?  How much is it likely to cost me?, I’ll be paying $7000 for the amp and the preamp..