why not go to uni and complete a degree in mechanical engineering? this type of degree will enable you to chase your possible dream but also provide firm grounding for other possible careers avenues.
My first job was retail. i then moved into hospitality where i managed a few football clubs, night clubs etc, then i wanted to go into advertising. 2 units later i was back behind bars loving the high after hours cash pay. i was then offered a small role in the company I now work for. We're a small comercial construction company where i work as senior estimator, business delepoment manager and project manager for commercial construction projects up to 10 million.
As you can see things change. Keep your mind open and try get involved with as much as possible. But remember practical skills are fantastic however when it comes down to applications you must provide written evidence like a degree. This is why Im back at uni completeing my degree now 6 years out of school. I have the referees, experience etc but now the piece paper is vital to continuing to climb the ranks of larger organisations.