Problems: Mesh on composite

Hey,

i'm also new at the topic of meshing and FEM. I'm trying to mesh a composite. I know, the geometry is really complicated. It's a transformer, which should be examined for heat transfer. In case of a accurate simulation i want to consider convection of the coils and the core to the oil (which causes a fluid problem) as well as radiation.

But even before i can worry about how to simulate the problem i don't reach this point because i can't mesh my file. I read some threads in this forum of how to mesh composites. I got some questions concerning this.
Ah, i created my geometry in Autodesk Inventor and imported it in Salome 3.2.9 as an .stp-file.

1. Is it really necessary to explode my geometry in solids and faces? I would receive 28 solids and some 600 faces. Recombining all the stuff is not a big fun.

2. Do i have to part my solids in blocks to mesh it, or is meshing also possible (for example tetrahedralization) , when i didn't create blocks? Or in which case do i need it and what the blocks good for?

Thank you for help!

ulf