Time to Replace Parts

[delawarelibraries 0]

This UO stops printing mid print, and has a dark drippy liquid forming on aluminum heater block. The hot end isolator tube looks like it's corroded, but I am not experienced enough to tell for sure. I have replacement parts, yet am loathe to disassemble hot end only to discover this is not the issue causing print problems. Can someone please look at the image and tell me if I should replace the parts, and which ones.

Thanks,

Delaware