Your quote is a line of hexameter, not an individual sentence.
The start of each line being capitalized does not mean that they are grammatically independent sentences.
The previous lines discuss the life of Balduinus, and he is also the subject of the verb on the preceding line.
The words hoc opus are the object, so the beginning of the line is: "[Balduinus wrote] this work".
What follows after the semicolon is a remark.
The sibi refers to Balduinus.
The remark can be translated, for example, like so: "May he have eternal retribution of life!"
(Note that it is retributio, not retributo.)
The exact wording is a matter of taste, but I hope this gives you an idea.