Hey Sophie
A couple of questions
1) Is this for 1 product, several, or many?
2) What do you want to achieve with the site? I know you want to see how the product sells, but what else will the site do?
3) How will customers receive the product(s)?
4) Where will your product info and pictures come from?
5) Have you worked out your realistic budget - the minimum you would like to pay and the maximum you have available.
6) Who is your ideal customer, where do they come from, and how will they find out about you?
7) What image do you wish to portray through the website?
8) Do you have the knowledge to customise a template?
9) Have you researched/purchased a domain name?
This and MUCH more is what a good website designer will work through with you. I'm not trying to push you into hiring someone, but IMHO you will get the best results by using the right resources.
A website is a business tool and asset, and what a visitor to your site sees is a vital part of your branding.
Heidi