Replace data in a table by deleting data and re-importing

Sounds like you just want to point your power query operation at a new dataset right? 

If you're using Excel, go to the Data tab, click Queries & Connections then double click on the query you'd like to change (on the righthand side). 

Now you should be in the power query editor. from, look at "Source" at the top of query settings. It'll likely say something like -> 

"= Excel.CurrentWorkbook(){[Name="Table1"]}[Content]" -> this means it's referencing data on THIS excel work book. so you just need to change that data and click refresh. 

If it says something like this -> 

= Excel.Workbook(File.Contents("C:\Users\YOURNAME\Desktop\Book3.xlsx"), null, true) -> then all you need to do is double click on "Source" and point it at the new dataset.