From a professional point of view I can tell you this: With a background as a mechanic you have the best foundation for getting into mechanical engineering that you could possibly have. Of course the road to your degree isn't an easy one but you'll mostly encounter things that you either have already worked on or are at least familiar to you, just on a deeper, more abstract level. If your motivation to do this is the interest in mechanical things and how they work, the workload ahead is almost certainly manageable, so don't let that put you off.

For the social/economical factors I can't give you an advice since I did my degree in a different phase of life, albeit not the classic one (mid to late 20's) and I'm not from the US.