It comes with the Compact SI transducer XNT 9 SI 180 T.
You can exchange it via Humminbird Customer Service IF it is unused and the mount package has not been opened. The $85 exchange includes shipping. An additional cost is shipping the Compact SI transducer to Humminbird.
The HD transducer is XHS 9 HDSI 180 T. It is 2" longer, has longer SI crystals that produce a thinner Imaging pulse. The thinner Imaging pulses produce sharper images.
It will improve the image quality for any SI unit that comes with the Compact SI transducer.
Your unit does not have DI. It has composite DI views that are generated by blending the two SI pulses. It will produce sharper DI since the SI is sharper.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1