Hola!
The easiest way to do this with Power Query, and probably the most optional, would be to use the "Replace value" option from the UI and basically call that operation multiple times. Is not as bad as you think, it's pretty straightforward and you can get it from the "Transform" group inside the "Home" tab. Just select the column that has the values that you want to replace and you can then do a "find and replace" operation similar to how you'd do it in word, excel or any other office application.
Now, of course that you can create your own pattern to do BULK replace operations, but those will run quite slow when you start hitting tens of thousands of records in which a workaround of a reference table would be needed which would add unnecessary complexity to your solution. I'm attaching that way to this reply, but, again, it'll run quite slow and even when optimizing it with Table.Buffer it'll still run pretty slow when compared to the way described in the first paragraph.
