Severance agreement arrived, need a second opinion after 15 years as a customer-service rep

My manager said the package is final, but the letter gives me time to review. It has been weighing on me all week. I do not want to leave money on the table. Did anyone negotiate and succeed?

An hour with an employment lawyer cost me a small fee and made me feel much safer about signing.

I asked for two more weeks and a neutral reference. They agreed to the reference and added a week.