Hi KingdomKerry,
I work in this sector, so if you would like more information, you can pm me.
To answer your questions,
1. To introduce an epos system to your business, you will have to set up each item individually unless you can get a spread sheet from your supplier and then import them to your system. If items do not have a barcode you can assign them a short code PLU(product look up) number e.g 100, 101 etc or you could generate a unique barcode in your software. Most Epos systems now give you the option of an item label printer, meaning you can print individual price labels with a barcode on it.
2. After you have created all items, you will need to do a full stock take. You could do this as you are going along but it will take that bit longer to get set up.
3. Most systems have plenty of reports to view your sales by department or sub department etc. Instead of looking at this information in reports, most epos systems will have an ordering program. In here you will specify a supplier and a date range. E.g Create an order for Supplier 1 based on sales from 01/09/2014-16/09/2014. You can then see how many you have in stock of all items supplied by that supplier, the sales for that period and a suggested order quantity based on the information. You will be able to over ride any suggested quantities or remove them completely from an order.
4. Writing off obsolete stock is usually done by a stock adjustment. You can then see a report of all stock lines adjusted by reason for the accountant at the year end.
Best of luck with it all and let me know if I can be of further assistance.