Find a more experienced and better equipped automotive a/c "specialist."

An experienced and skillful a/c tech will find a way to thoroughly test for leaks WITHOUT doing such exploratory surgery. There are many different leak finding methods including UV dye and less common but maybe most effective is charging with a few ounces of R22 and dry nitrogen. R22 is more easily detected by an electronic leak detector.

18.5 hours is a lot of labor money to spend on an experiment.

Good luck,