fonts are located at \system\font in the firmware, and they're bitmap based fonts that will be always rendered as such, so forget about true type fonts or clear type or whatever. there's a .TTF font available there, though, but its function is to act as the default typeface for the text reader and it's not used anywhere else
since you're seeing value in how "tech guys" (lol) perceive your cheap china made console (which it is
) instead of the amount of things you can do with it for the price you paid for it, can i ask you why the hell you bought a dingoo in the first place?
It's possible but not worth the amount of effort it would require, probably easier to write a nicer looking menu from scratch and just replace the inbuilt one.
it's way easier than what you believe. it's a tiresome process, though