What level should you enter a college when attempting a career change after obtaining a bachelor and master degree in an entirely different field?
You should visit a college advisor for the new field (if it requires more education) and see what will carry over from your previous education. At worst, I imagine you would be a junior, unless you have to pick up all of the math for the new field. For example, at one point I thought I would add math to my subjects for secondary teaching. That entailed taking more classes than I could do at once since the skills all build on one another. For something that is a practical vocation, a junior college or trade school should do the trick.