Most of the decent shop fronts have a weight section when you initially enter the product details. This interfaces with shipping cost (by weight) tables you've created so when multiple products are ordered it calculates the gross weight an automatically works out the shipping costs, plus product cost and duty etc. Build a little margin in the shipping costs to cover materials and odd sizes so that in most cases you make a little extra on the shipping which covers the odd time where you lose out due to the size of the item.
Another nice feature of most carts is they also manage the stiock control and can order more stock if you want it to and remove the product from the website automatically when you run out.
If its done right, you sit back and wait for the orders to roll in and just pack and ship. If your turnover is high enough, you hold your stock in the shippers own warehouse and they do all that for you too. So all you need to do is count all the money your making.
OMG! But hey if it works!! What you should look for is someone that would do an overhaul and transfer all the existing data to a decent web-based database server and provide you with a simple web-based administration tool so you can add, update and delete products. There are eCommerce products like Actinic that would do all of this for you but you'd still need to get someone to make it look nice. Try to remember that the more you spend now the less you'll have to spend in the long-term. As your business grows you'll have different requirements from the site so best get them specified and designed into the system now.Also look at osCommerce, it's free and pretty easy to set up.
