I'm assuming you mean an automotive mechanic or do you mean Plant Engineeering mechanic? In either case, the first question is are you qualified for the job? What is you experience background in this field? Can you handle the economics of the 2 1/2 year wage progression which starts at 70% of the current top scale rate and progresses from there? I don't know your locale so this may be different where you are. In all probablity, about all cases whether auto or PE, the job will start off as night work and unless you hit the cycle just right, odds are you'll remain on that shift for many years to come. Are you in a position to handle that?
Ask about the current seniority in the shop because if it's all low seniority this could mean a long wait on the nightside to move up. Also unless it's a new facility or has experienced a large retirement cycle, a larger low seniority workforce may signal a higher than normal turnover rate. Ask yourself why and try to learn more on this. Ask the supervisor straight up about the history of the shop in an attempt to learn more without appearing too nosey or pushy. Watch his/her body language during this process to see if it appears something is being withheld. Look closely at the mechanics in the shop ar how they carry and conduct themselves. If possible, remember some faces and if close to shift change, (ask supervisor during interview process what are some of the scheduled hours to get an idea of how the job timeframe works to get an idea of when the mechanics you saw might get off work) talk to them and especially the more senior ones. They are a better historical resource. One caveat though in talking to employees, do not do this while they are on the job or in the workplace. Do this when you both are really on your own time and the other warning is talk with several if you can. In talking with only one you could talk with a bad apple or someone with brown colored glasses. Those aren't the ones you want. As much as employers like to think, this process is not a one way marriage selection. They may want you but in the end you may not want them and nothing lost if you walk before saying I Do!
Getting back to personal and family impacts, if you are married, have a family or significant other, you really need to discuss this job and all it's aspects in great, great detail. Night work requires many lifestyle changes that impact others around you and if there is any doubt of them adjusting or even yourself then forget it and go elsewhere. Do you have a family lifestyle built on events that take place in the evening, ie kids sports or other family involved activites, then again, I'd forget UPS. If you do take the plunge, expect the worst to always be the case. It won't be mind you but when it's the reality, it's already a given in your mind to happen so you just roll with it.
I don't mean to throw a bucket of water on your excitement but you need to be realistic that this job will require you to make some sacrifices in order to be successful. If you come in, come in with eyes wide open and you may not like the hand dealt at time but mentality you're prepared to adjust. Otherwise you'll just be miserible and unhappy.
Good luck!