As far as suppliers, Grainger supplies Mexico. The engineers in the plant will know where to get stuff.
Someone else mentioned you'll need a work permit. The plant will need to provide you an introduction letter and you'll need to keep the permit (FMN) with you in the plant. Occasionally immigration will come into plants and verify all gringos have their permits. The plant gets fined if they don't. You also need to remember to turn it back in when you leave otherwise you'll get heavily fined the next time you go to Mexico.
I work about 3 months a year in Mexico doing machine installs and upgrades. I like the people and the food very much but the work culture is very different. When they say, "the machine is ready for you to install" it really means, "we've moved it off the dock". It's likely still on the skid. It certainly won't be in place, level, and have utility drops. Something as simple as an air disconnect and electrical outlet can take days. Everything happens slowly. You have to be very patient and just accept it. You can't change it. You can get frustrated and yell & scream but all that's going to do is raise your blood pressure - it's not going to get anything done faster. When you go back the next time to work on the machine you'll find sensor wires with 6 crude splices or sensors missing completely because they didn't want to buy another one. They're clever enough to disable sensors in the software if it means not spending money on a replacement part. I've learned over the years to not take personally what they've done to "my" machine. It's not mine anymore - it's theirs. When I schedule a trip I let them know when I'm arriving and when I'm leaving and that I will not stay longer if they haven't prepared for me. If I spend a day doing something that they should have before I arrived like leveling a machine and hooking up utilities that's one less day for me to get the job done that I came there for. I know that sounds like lousy customer service, but I've given up too many weekends and time at home for that sort of thing and I won't do it anymore. I also won't work on a machine that's had safety interlocks removed or disabled. I'd feel terrible if anyone was ever hurt by one of my machines even if it wasn't my fault, so I won't knowingly put a machine back in service that isn't safe. I can't control what they do after I leave, but I damned sure won't leave it unsafe.
As far as danger, Mexico isn't one monolithic place. There are nice areas and bad areas just like the US. The farther from the border you go the safer it'll be. I'd have no problem walking around many parts of Monterrey. Reynosa or some other border town, not so much. It's like the difference between Denver and Chicago. There are many areas in Mexico where I feel as safe as I do in my little midwestern suburb at home. I took my daughter to Guanajuato and no qualms about letting her wander around alone after dark.
