If it is a kit to assemble your self it is no problem with customs - Kits are also excluded from the CE - marking.
Thus if there has to be soldered something or two parts just connceted together or the PCB has to be mounted in the housing it is a kit (Bausatz) and is not affected by a missing CE-sign.
(I think it is a parallel to the FCC-rules in the US where you have so called kits where you have to put just one transistor in a socket to complete a rig - than this device has not to be FCC-certifed).