Moving a glider to Europe

A friend of mine is thinking about moving temporarily a US-registered
glider (DG300, with its trailer) to Europe. The final destination is
Italy, but the entry port can be anywhere.

I heard that sometimes this can be tricky, could end up with a bunch
of duties to pay and/or the impossibility to fly the plane while
there. I'm sure someone else has done it before, and I would
appreciate any suggestions about where to entry (Germany? Holland?
maybe Slovenia?) and the paperworks necessary.

Thanks in advance