More Versatile Find and Replace - Find and Replace Within a Cell

Hi there folks,

I'm currently looking for a solution to this issue.
I have a spreadsheet of numbered lists within many cells.
For example,
Within one cell I have:

1. On a plane
2. On a boat
4. In a car
5. Many other vehicles

These lines are separated with line breaks.

Then in the next cell I have more numbered lines starting again from 1.

This spreadsheet is huge and I'm looking to be able to replace any words or phrases in a selection.

For example in the above case, I would wish to change all instances of "Many other vehicles" to read "Alternative transport", but the issue with the standard find and replace button is that it searches per cell, and not within cells. I want to be able to run a macro or use excel's functions to look through the sheet for a word or phrase within each cell and if it's present, replace it with another pre defined string of characters.

I'm really looking to be able to understand how the solution was developed so a few pointers and an explanation would be great.

After this problem has been sorted, I eventually want to be able to look through a spreadsheet and instead of replacing specific phrases, I need