Basic startup help needed

Hi All
I am in the planning stages of my company which will be selling some gift items online and I am stuck with some basics that I need help on:

Product IDs
I will be using an asp shopping cart which allows to handle all the payment side of things online. The shopping cart uses microsoft access database in the backend which can be upgraded to mysql. This requires unique product IDs for products. I have never been involved with retail linked items so I dont know how I should create unique product ids.
1. Should they be something that can help me identify where the product is from and who supplied it (they will come from different countries) so I can reorder?
2. In cases where products are items like handicrafts which will mean new products everytime I order, do I keep assigning new ids to them or reassign old ones?
3. Does having a bar code make it easier rather than trying to create an id with numbers and letters everytime?

These are some of the questions I am very unsure about. I will really appreciate it if anyone can help - apologies if this is really basic stuff but if there is somewhere on the web or books that can help overcome this problem, please do let me know.

regards, jkk