You apply at a company and interview for the job. It’s not great pay and it’s moderately stressful/difficult work. The only way to make a lot of money is to be a supplier for some very instrument and having tons of connections.

You just want a programming/engineering background, pickiness depends on the employer.

My training is in Business (Batchelors) and Operations management (National Diploma), and I've been in engineering my whole working life (Started as a daftsman). But we have guys with high school only who have learned on the job and are good at it. Work we do on these lines requires specialists in various fields, I could'nt sort a faulty production line out on my own. If you can program (or just read programs) you have the hardest part behind you. The rest is reasonably simple mechanical ability. Getting your foot in the door is probably the hardest part. We started by specialising in one important aspect that all these lines have in common, and built around that.