Question for service technicians: My 1999 Dodge Neon leaks oil...?

I have replaced the oil pan gasket and the oil pan. The shop that did the work had to re-do the oil pan gasket because it was not done correctly and continued to leak. The technician told me that he "really made sure" that the gasket was in tight and even glued it in there. I was told that everything was fixed and that I should NOT have anymore oil leaks. I am still leaking oil, so I took the car back in. This time, they say that the rear main seal is leaking and they mysteriously don't have the tool needed to fix it. It seems strange to me that I was told I wouldn't have anymore leaks, yet a week after they work on it, the seal starts leaking. Is this just an issue of the car being higher mileage or is it possible that they caused damage to the rear main seal when they worked on the oil pan and oil pan gasket?