Create App Scripts and Macros for Google Sheets

Our team is creating a shared spreadsheet that will have 1-hr, 6-hr & 24-hr timers on the same or different sheets. The timers will be reset with a key command. The project we need you to create is as follows:

The trigger is:
1. A key command such as ctrl + alt + shift + 1
The function is:
1. Enter start day and time in cell C3 and turn the cell Green.
2. In one hour turn the cell Red and send an email to ----------

The timer can then be restarted by entering the trigger in the same cell again.

This is a gig that will lead to many more.

When applying, please provide an estimate of the number of hours it will take you to create this functionality.

Thank you!