A bit more information would be helpful.
Is it just the name of the field that's an issue where the starter solution names the field "Product ID" and you'd prefer to call it "product no."? There's a very good chance that the product ID is an auto-entered serial number in the starter solution. If you use it as your product number and simply rename the field, you'll need to go and and change the "next value" setting on the auto-entered serial number to something larger than your largest existing product no. value.
And this assumes that your product no. is a strictly numeric value and not alpha-numeric.
If I put our Product No. in the field "Product ID" then when it gets previewed that field is not seen. Ideally I'd like to be able to delete the Product ID field and have the Product No. field on our invoice allow me to insert the product number in and then the lookup for the rest of the product information appear. When start putting information on the invoice aside from the customer information we will enter the product number. I can't imagine why there is a product ID that would be a number different form that. We have over a hundred products that will be growing.
I did change the Product ID from a serial number to nothing for now. The Product numbers will have both numeric as well as letters.
I attempted to send you a message but it wouldn't work.
Not a good idea unless you are also willing to make a number of other changes. That ID field is the glue that holds everything together, if you look at the relationships graph, I predict that you'll find that the ID field is the match field in several relationships and it needs to be an auto-entered serial number in order to enforce unique values.
What may work better is to add the Product No. field as a separate field to products and whatever table serves as the line items for your invoice and use a different occurrence of Products linked by Product No. as a way to look up the Product ID--which then links records as they should be ID and pricing info can be looked up from products.