What kind os issues are you having and what kind of fault codes is the Progressive giving you?
Do you have the remote display with the bypass switch. That forces the relay closed, no matter what.
I had a HW30C in my motor home but decided with the trailer to go to a portable unit so I could elect to not use it, and if I sold the trailer it would not have to be replaced with the next RV.
All you need to do is take the wires from the shore cord and splice them to the wires you remove from the HW30C. The splices need to be inside a box and a good heavy splice (not wire nuts on that fine stranded shore cord). I would use appropriately sized Polaris connectors or similar to make the connections.
Wire goes in each end and there is a set screw to tighten under each of the plugs, they are made in many different sizes and styles.
Charles