> at 39 years old I am probably past the point of going to university to actually study.

That largely depends on your financial situation. If you have a strong technical background and you've already secured your retirement you could certainly do a masters or phd. But if you aren't financially secure then yeah, accepting (somewhat worse than) minimum wage for the next 5 years followed by a high degree of uncertainty sounds like a really bad idea.

That said materials science is something of a bastard child of inorganic chemistry, applied physics, and engineering. The theory side of it can be absolutely brutal. Before embarking on an adventure I'd suggest looking over the coursework for physical chemistry to see if you can handle the quantum mechanics stuff.