Determining the value of a pension can be difficult. On one hand, you could make a rough guess. But if you want to get a more scientific value for the sake a fairness, using an actuary is a good idea.
What is an actuary?
For the most part, an actuary is a person who is skilled in statistical and financial analysis. Actuaries have to take many difficult tests for their certifications. Many are hardcore math people.
An actuary will perform complex calculations involving life expediencies and the rules of your retirement plan. The output will be some present value of your retirement plan.