Welcome to WebmasterWorld, MaBetts87 :)
It's possible to optimise pages with very little text on them, via considered use of title tags, headings, internal linking and external links. But this is often an unenviable task and is likely to be difficult for someone new to SEO to achieve.
I would encourage you to ensure every page has at least a few sentences of unique text, and that you pay particular attention to the elements mentioned above.
One of the key advantages of having greater amounts of text on a page is the ability of such pages to attract traffic for a diverse range of keywords, and also to pick up niche traffic. For many new sites or previously poorly optimised sites, niche traffic can be vital in order to maintain a reasonable volume of referrals in the short-medium term.
If writing new copy is out of the question, then at the very least you will need to ensure that the copy you do have (i.e. the product descriptions) is well-thought-out.
I'd also consider taking a step back, and looking at a 'content strategy'. What do people who are likely to buy these products search for? Is this content that can be accommodated on the existing pages, or would they require additional sites, or participation in external sites? What resources are available to create the necessary content?
Once you know what content you need, you can then prioritise creating it, based on the 'most important' products. What's important is likely to factor in both popularity with your target audience, relevance to your specific site, and profitability of particular products.