I've found over the years there are people who operate equipment and then there are equipment operators, there is a huge difference, some can never really be taught anything, others don't need to be taught, they are naturals operating equipment and learn on their own as they go.
Before you sign up for a Union, you might want to study up and do a lot of reading of the pros and cons of Unions and ask yourself the question, "where do you want to be in 20 years and what do you want to be doing" Then ask yourself, where do I plan on doing it, if you plan to stay in a Union area, that's fine, if not, a prior union association in a non union area would be a huge hindrance.
If your self motivated, show up for work, are willing to work, can pass a drug test[which today is the huge part of being qualified for any job] and can do what your told, your leagues ahead of anyone else your age and can literally pick for who and where you want to work, all the above will also determine what pay and benefits will be starting out.
As for CDL training, myself I'd avoid it as long as possible, everyone is looking for a CDL driver and if you have a CDL no matter what your hired for, you'll end up in a truck no matter what level of experience you have or interest in driving truck. This is fine if that's what your interested in, but if you want to be an equipment operator, just be aware your going to be driving a truck instead.
If your heading into heavy equipment operating, you might be doing it at the most opportune time in history. With older folks retiring, most not being able to pass a drug test, a whole modern concept of "I really don't have to work, I'm entitled", wages and benefits shy rocketing, able work force shrinking, interest in heavy equipment dwindling. The hardest decision you might have is who do I want to work for and what do I want to be doing 20 years from now and where at.
As for training and what's needed, that would depend on who's hiring you and what they require, ask there first.
As for CM's offer, all jokes aside, myself I'd consider it, but the harsh reality is, there are probably dozens within driving distance of you now that would be willing to offer you a very similar deal.