NI has an example provided for J1939 here somewhere that is an example of using the transport protocol defined in J1939 to send or recieve data longer than 8 bytes. The example is based on the frame API, which precludes you from using the channel API with a CAN database on the same port.
DMC recently developed a set of J1939 protocol drivers for LabVIEW which are based on the NI-CAN channel API. The drivers are written in LabVIEW just like the example, but provide functions at a layer above the base CAN channel API layer. This allows the simultaneous capture of data from both J1939 packets which are simple broadcast CAN frames, or more complex transport using BAM, including extended data frames.