You can replace the broken mast by first removing the plastic cap nut. Then use an open-end wrench on the flats at the bottom of the mast.
If the base and lead-in wire needs replacement, access can be gained by removing the outside air intake grille and working through the opening in the cowl. See attached pages from the shop manual.
The entire shop manual is available on this site at:
Thanks for help ive managed to get the old whip thread out of base now trying to track down new whip ive sorced one in states 50 odd dollars but want that again to ship over a 100 dollars for a new whip is a lot.