Usually when buying something like that for your personal use they don't charge import fees. I have never paid a penny of duty or tax on anything ever. Just order it and it will be delivered no problem just pricey freight bill. I also find Maryland Metrics to be high on its of special order items. Just get on with it the sooner you order the sooner it will ship.
It depends on value, who and how it is being shipped, and who the carrier is. In my own exp. Ive only been charged duty by fedex and its been nominal, a few percentage points at most.
I would call customs and ask them. It is hard to say what can and will be charged there are new laws that have just been put in place. One example is a bearing for a British made cycle Import duty went from 32 percent to 74 percent the reason... we have usa bearing companies but NONE make that bearing.
JFYI ot costs us $135 to ship a 30 pund crank to london.
$700 for a 400# bike from london to here.