My question involves collection proceedings in the State of: Delaware

I have a credit card debt that was sent to a collection agency. The agency sent me a form letter saying they would settle for 40% of what I owed and consider the debt paid. I'm willing to do that, but I was wondering if I needed legal representation to make sure they honor the settlement. Because this might just be a ploy to get anything from me and then go back to harassing me for the rest.

So I was thinking that I either need advice on how to ensure their offer is official, or get some kind of legal help. Do I have them send me a real letter signed detailing the terms and then take it to a notary or something along those lines? Or should I get legal representation? If so, I'm hoping not to have to pay too much for it. Any advice or ideas?