replace "0.00" with text but seperate 4 shipping + products

I know it is possible to replace 0.00 wherever it is on the website be it product or shipping with your custom text. I have this at the moment on my site

however, I want a separate text replacing 0.00 for products and shipping

some of my products are on 0.00 as customers need to pick options so I have the words "pick options"

if 0.00 is on shipping example free shipping is applied then "pick options" is not what I want so I would like the word "free shipping"

Whats the best way to do this?

Thanks