If you have the old McGill Oval switches then Contura rocker switches won't fit the existing rectanglular hole.
If you have these you should plan to replace all with a new switch panel...
There are a lot of variations in switches.
Switches are different depending on what they do. There are SPST, SPDT, DPDT.. On/Off, On/Off/On, MOM ON.....
There are Indicator and there are Illuminated and there are illuminated indicator....and even backlit....
Look at the NewWire site. Get an idea of style.
Get an understanding of which style and type of switch you need.
Contura rockers of all types are availabe at any West Marine and on Amazon.