First congrats on choosing the finest RV antenna made at this time. IF the arms are bent and broken then its a bit more work however the job is still fairly easy.
To replace the head only,disconnect the coax. Then you pull a couple pins. (Good time to replace the above-the-roof coax) and re-assemble in reverse order.
There should be a coax connector AT or Near the roof covered in caulking.
IF you need to replace the arms.. Do the above, remove one Set Screw (Allen type) inside and carefully remove the nadle, springs, washers pointer ring etc.
The up on the roof lift out the antenna assembly and "Drop" (gently) the new one in the same hole. Replace Coax as above. Re-assemble inside, KEEP Ring and handle you may need them some day.