Have you read the seller's feedback? It's important to see why a seller got the low ratings that brought their overall rating down. Sometimes they are given low ratings for fairly minor things, like slow shipping or a slow response to questions, and other times they are given low ratings for more important things like sending bad or wrong products and then refusing returns/refunds on them. Also, how many total ratings does the seller have? It's important to look at that too. If someone has only done a few sales and one of them was rated poorly for a minor reason, then their overall score will be quite a bit lower than someone who has done a lot of sales but has made several bigger mistakes. So keeping that in mind and reading the feedback should help you decide.
I personally buy a lot of stuff from Amazon, and I would feel fairly confident about buying from a seller with 97% positive feedback there. However, the seller ratings scale varies a lot from site to site, and different sites offer different degrees of protection for customers, so I'm not sure about that rating on other sites. Good luck though!