I have done this several different ways over the years. One recent one was for a simple web page that will allow you to upload a CSV (ASIN in specific column, or just single list of ASIN, one per line). That then replaces the list (entirely) in a MySQL table.
Separately, a CRON (scheduled) job goes through the list once a day and gets the additional information required from the MWS API - obviously needs your credentials and an API key - I can step you through this.
There is another simple web page to download the latest dataset from the server, based on the latest list of ASINs uploaded.
Let me know if you are interested.
Regards,
Richard