hi there i had a look at the template and it could be difficult to add fields to these. it would take a lot of moving and redesigning of the template. it can be done but if you are unsure it maybe better to create your own. also to create the field you will need to have access to the table on which the template is based. if you designed your own, then you can then put in your id field as a primary key (this gives each product a unique number which cannot be re-assigned to another product). this will allow for easier queries and reports later.
if you want anymore help you can mail me.