Received settlement letter from Capital Management Services. Debit is mine and I'm willing to pay. How do I proceed?

I paid off my car about 9 months ago, but was informed of a $432 collection of accumulated late fees over the years. I had every intention of paying it off when I had enough money saved. Apparently, I waited to long and it went into collection. And I've not received my title. I recently received a letter from Capital Management Services, LP saying that I can settle this debt for $64.90.

I almost paid the settlement via their website, but decided to search more on the topic of settlement offers.

I know this debt is mine, so there's no question about it. I've briefly looked through other posts about sending in a debt validation letter as well as sending a settlement letter to ask the collector to state they won't sell off the remainder of the debt and whether or not this settlement will clear me.

I'm still confused as to exactly how to proceed. Even though I know it's my debt, do I still need to send a validation letter? Do I contact ???Capital Management Services with a settlement letter? Do I contact the current creditor they say it's through? In this case, the letter I received says it's through Arrow Financial Services, LLC.

Thank you!