How do you contemplate delight you get due to action that leads to detachment?
how do you contemplate this delight?

From MN1, we know that...


  MN1/en/bodhi ...delight is the root of suffering...


Therefore, rather than contemplating and nurturing delight, it may prove more fruitful to contemplate emptiness:


  MN8:3.6: A mendicant gives up and lets go of these views by truly seeing with right wisdom where they arise, where they settle in, and where they operate as: ‘This is not mine, I am not this, this is not my self.’


MN8 is a wonderful sutta that explores the relationship between practice and action that you have brought up in your question. Notice that what is contemplated is NOT delight:


  MN8:12.30: ‘Others will be stingy, but here we will be without stinginess.’