For the duplicate side of things if the data is in order, you can pick a column, and use:
Run that down (Autofill Down)
if it's not in order, then use:
That will make it easy to identify where you need to act. Everything that has a 1 is a duplicate.
For the balance of the request, you could record the requirements in excel, and then replay it as required.
If you're not proficient in VBA code, then try this:
Best VBA beginners book
Good Excel VBA books for beginners?
Best of luck