Finalizing Model for 3D Printing

Hi Everyone,
I need some advice on finalizing my model for 3D printing. I want it to be multicolored. It is currently separated into multiple different objects like Dress, Body, Eyeballs, Eyelids. I think for 3D Pritinh I should merge every single object into one. But I’m not a blender expert and am having a really hard time trying to do so. Because all of my Objects intersect. I tried using the boolean modifier, but results don’t come out as wanted. Is there some kind of modifier or action that will remesh only the surface of a group of objects? If not whats the best way to go?

It’s supposed to be a present for a friend and needs to be finished soon. If I’m not able to fix it in time would someone maybe be so kind to help me with my model?

Lots of greetings

You could post your blend file and maybe someone could help you?

Yes, sure.
Here it is.

Thank you very much in advance!

Has someone had the chance to look at my file yet?