Check all the connections before replacing anything. There should be a connector at the base of the mast. Check for oxidation of all connections including at the top of the mast where the aerial connects. Normally the central wire of the cable is soldered to the central pin of the connector. if there is not a good solid electrical contact the radio will either not transmit/receive, or it will be cracklely.
If you do replace the aerial I recommend you replace it with one that incorporates a wind vane.
If you plan to replace the cable, then the mast will need to be unstepped and, depending on the way the mast is designed may require some dissassembly of the top of the mast to get the cable through.
I don’t think the coaxial wears out as such, but if it is damaged such that the shielding around is damaged this can cause interference and if fills with water this may stop the signal getting through.
If you have AIS, then you will need an antenna splitter.
I hope this helps.