You can try rotating the dipstick while lightly pulling on it, but chances are it won't come out. I wouldn't worry about the end of the dipstick if it pops off the cable, but if the cable breaks in the middle, the pan will need to come back off. Frankly, the shop screwed up and should come good for the repair. Maybe if you go back you could work a deal to remove the pan and free the dipstick.