Deduplicate mailing file of 20,000 records in Excel

Very simple job - we have about 20,000 records that need to be deduplicated. The data includes name, address and zip/postal code. We want to remove duplicate records. You can't just use the zip code to de-duplicated as some people have the same record (e.g. same street), so you will have to also go by the surname. Once the de-duplication is done, in addition, there is another file of 500 records that we need to remove from the complete 20K file. These are names of people who have previously bought the product in question, so we need to remove these names from the file also.