Adjustments to a magento 2 module

we are in need of small tweaks to a magento 2 module ( preferably as a separate module that extends this one)

I can not upload module here but based on below I can share the zip with you

- module is a delivery date module that ads a calendar at checkout
- module has a label in configuration which we have a Delivery Day - the label is addded using some ui components I think, not static template files
- module is adding data in API under a delivery_day field

What we require
- we have also a collection method - carrier whcollection - method collection
- we would like to adjust this so that
a) if collection method is selected - label and placeholder for the calendar at checkout are changed to Collection Day / Select Collection Day - example of how it looks now below.
b) add in API - collection_day - allongside delivery_day and complete as needed based on the delivery method chosen ( for any non collection method - leave collection day empty - add data in delivery_day // if collection day is selected - then reverse)