I'm familiar with that VG3400, we threw one away at work. You will absolutely have to dump the spindle at minimum, as they use a proprietary tool that threads in on top of the spindle, and only come in small engraving points. The belt drive is just awful, and the adjustable spring tension collar won't work for actual milling. The rest of the machine is built like most small routers, except not much Z travel.
Tiny aluminum can probably be done in it after mods, but only with very small tools, like <1/8". If your wanting to do large brackets and whatnot, a much heavier machine would be a better choice.